Waves of Invasion and Recovery: Insights from 57 Years of a Monitoring Program on a Large River

The Long Term Illinois River Fish Population Monitoring Program (LTEF) is a standardized sampling program that began in 1957. This fixed-site, annual monitoring documents a profound change in the fish assemblage of the Illinois River Waterway, including the collapse of a common carp invasion, the resurgence of sportfish and native species, and the beginning of an Asian carp invasion. The extensive spatial and temporal reach of the LTEF make it well suited for documenting the strong changes in fish assemblages that were coincident with implementation of the Clean Water Act. Emerging challenges include improving sampling precision and comparability across sampling programs. We consider how trends in the LTEF indicate ways to balance long-term programs with the dynamic needs of fisheries management and ecological research in large rivers.