Fish assemblages and biotic integrity of a highly modified floodplain river, the Upper Mississippi, and a large, relatively unimpacted tributary, the Lower Wisconsin

摘要: The Upper Mississippi River is a dynamic floodplain river that has been largely transformed by navigational levees and dams since the 1930s. pools upstream of each dam are lake-like only about upper third reach retains riverine character. In contrast, Wisconsin not managed for commercial navigation today its lower 149 km represent one least-degraded large reaches in central North America. Riverine both rivers have similar macro-habitats including numerous islands, side channels, connected backwaters lakes. this study, shoreline electrofishing samples were collected during summer 2002 2003 to characterize resident fish assemblages. We compared species abundance, biomass, biotic integrity along main channel borders between Lower River. expected that, absence environmental degradation, composition structure would be rivers, types within river. Nonmetric multidimensional scaling redundancy analysis revealed River, unlike characteristic non-riverine habitats. consider assemblages indicative impairment. sites had more variable than Analyses index scores showed condition was excellent whereas rated good fair. conclude differences two consistent with direct indirect effects navigation. This study demonstrates utility integrity, an inexpensive rapid bioassessment tool, detecting change ecological health on world's largest rivers. Copyright © 2006 John Wiley & Sons, Ltd.