The Effects of Improved Water Quality on Fish Assemblages in a Heavily Modified Large River System

摘要: A long history of human alterations has affected the hydrology, physical habitat and water quality most large river ecosystems. For more than a century, Illinois River Waterway been subject to channelization, damming, dredging, agricultural runoff industrial municipal effluents. This study evaluates how subsequent improvements in have influenced long-term changes fish assemblages (1983–2010). We used five metrics characterize assemblages. These depicted shifts abundance biomass predatory native fishes species richness. Random forests (RF) multiple linear regressions (MLRs) were relate individual weather variables, with primarily account for inter-annual variation. Model performances varied spatially among (0 ≤ pseudo-R2 ≤ 0.73 RF; 0.10 ≤ adjR2 ≤ 0.88 MLR), but dissolved oxygen, un-ionized ammonia clarity often best predictors. As distance downstream major pollutant sources increased, became less important explaining important. results indicate that improvement largely accounts assemblage recovery system, although within some reaches we examined, had substantial compounding effects. The could be prioritize variables monitoring aid predicting responses future climate. Copyright © 2015 John Wiley & Sons, Ltd.