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

Abstract

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

Long‐Term Change of Fish Communities in a Polluted Watershed: Does Cleaner Water “Act” on Fishes?

“…Evidence that the CWA or SMCRA have benefited lotic fish communities is surprisingly lacking throughout much of the United States (Adler ; see Rahel ; Parker et al. ; and Perkin and Bonner for notable exceptions however). The paucity of positive outcomes stemming from these legislative measures can be traced to several causes.…”

The effect of a large-scale irrigation scheme on the fish community structure and integrity of a subtropical river system in South Africa

“…Data from the national river monitoring programme were only available for certain years, were not expressed into a fish biological index and had no concurrent water, sediment or habitat data making it impossible to link fish community changes to individual environmental parameters (RHP, 2003). It has long been accepted that the ability to link long term community changes to specific water quality parameters aids management programmes and ultimately can improve river systems by creating sustainable utilisation and management systems (Parker et al, 2015). This lack of data on fish communities linked to environmental quality is a major problem in South Africa as well as in most developing countries due to a lack of implementation as well as a lack of sufficient funds.…”

“…Long term monitoring programmes are able to characterise the inter-annual variation present in fish and environmental parameters (Parker et al, 2015). The variation in fish communities can be driven by multiple factors like climate, rainfall, flow volumes, water quality and potential anthropogenic activities (Parker et al, 2015).…”

Implications of an invasive fish barrier for the long‐term recovery of native fish assemblages in a previously degraded northeastern Illinois River system

“…Water quality and habitat improvements have facilitated dramatic increases in native fish richness and community structure in the IRW since the Clean Water Act (Gibson‐Reinemer et al, ; McClelland et al, ; Parker et al, ). The transition in the Des Plaines River from almost river‐wide community clustering in 1983 to eventual community differentiation among sites illustrates the increasing variability inherent with improving water quality and habitat availability.…”

“…Heavy industrialization and urbanization severely diminished upstream fish diversity and abundance in both rivers beginning in the late nineteenth century (Gibson‐Reinemer et al, ; Hammer & Linke, ). The Clean Water Act of 1972 brought about water quality improvements (especially reductions in un‐ionized ammonia; Parker, Epifanio, Casper, & Cao, ) that facilitated better conditions and increased fish diversity. Additionally, 12 dams have been removed across both rivers since 2008 that substantially increased longitudinal connectivity for native fishes (Pescitelli, ).…”