Ecological Recovery of a River Fish Assemblage following the Implementation of the Clean Water Act

Abstract

The twentieth century spanned an era that included nadirs in environmental quality and subsequent efforts to improve ecological conditions. The Illinois Waterway, a large river system in Illinois, experienced prolonged degradation followed by a dramatic recovery. In the 1950s, a standardized sampling program was initiated that has continued for six decades. The resulting record documents profound ecological changes, demonstrating the potential for river ecosystems to recover following the successful implementation of large-scale policies, notably the Clean Water Act. Over six decades, native species diversity has increased, and one of the most prolific invasive fish species has collapsed. In addition, the sampling record highlights the recovery of socioeconomically valuable sport-fish populations. We examined the causes and consequences of change in a large river using data from a long-term monitoring program with unique spatial and temporal extent. The trends documented in the Illinois Waterway are relevant for the restoration of river systems worldwide.