Spatial and temporal patterns in fish communities along the Illinois River

Abstract

Abstract – Fish abundance data from a fish population study (1957–2000) on the Illinois River, IL, USA were used to assess community structure. There was considerable variability among reaches and years, but three distinct fish communities were identified encompassing both temporal and spatial aspects. Temporal community shifts in the upper half of the river created two distinct fish communities, one prior to 1983 and the other after 1983. This is believed to be in response to improved water quality, albeit the responses were delayed for several years after policy implementation. The third group (Lower River) was spatially separated from the two upper river groups. These differences may reflect a combination of water quality (e.g., pollution) and habitat issues (e.g., geomorphology), common to many regulated rivers. Fish community responses in larger rivers may have considerable temporal lags after implementation of management or restoration activities that warrant strong consideration during any planning process.