Illinois Natural History Survey - University of Illinois

Aquatic Resources Monitoring in the Upper Mississippi River Basin

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The Upper Mississippi River System (UMRS) encompasses nearly 1,300 miles of waterway including the Upper Mississippi River, Illinois River, and several other important tributaries. This system is home to a wide array of fish and wildlife species distributed among diverse habitats such as channels, backwaters, sloughs, wetlands, and adjacent uplands. Historically, these floral and faunal communities have been important both ecologically and economically.

The Illinois River provides a good example of the economic value of this system because this river alone accounted for about 10% of the United States' inland river commercial fish harvest in the early twentieth century. However, management of the UMRS for human needs (e.g., navigation, flood control, etc.) has changed many of the natural dynamics of this ecosystem. This has created a tenuous balance between biological and human needs, the effects of which are not well understood. Despite these conflicts, the UMRS has been identified as one of a select few large floodplain ecosystems with enough integrity to possibly recover from these changes. To better understand the recovery process, long-term data are needed. Long-term information from large rivers are a rare but valuable commodity because they allow assessment of community responses to environmental conditions and also provide insight into management practices in these dynamic systems. Fortunately, such data do exist for the UMRS in the form of two projects currently being conducted by the Illinois Natural History Survey (INHS): the Long Term Resource Monitoring Project (LTRMP) and the Long Term Illinois River Fish Population Monitoring Project, also known as the Long Term Electrofishing project (LTEF).

Since its creation by the 1986 Water Resources Development Act (Public Law 99-662), the LTRMP has been conducted through a collaborative effort among the U.S. Geological Survey's Upper Midwest Environmental Sciences Center (UMESC), which administers the program, and five states (Illinois, Iowa, Minnesota, Missouri, and Wisconsin) with funding provided by the U.S. Army Corps of Engineers. The mission of the LTRMP is to provide river managers with the information needed to maintain the UMRS as a multiple-use large river ecosystem. The long-term goals of the program are to understand the system, determine resource trends and impacts, develop management objectives and alternatives, and manage the large amount of information collected.

Six field stations have been established throughout the UMRS to document long-term, system-wide ecological trends encompassing five separate 25-30 mile reaches of the Mississippi River, including Pool 26 studied by INHS staff at the Great Rivers Field Station and one 80-mile reach of the Illinois River studied by staff at the Illinois River Biological Station (La Grange Reach). Currently, the majority of LTRMP efforts are focused on monitoring fish, water quality, vegetation, and benthic macro-invertebrates. However, other research projects are also conducted as needed. Standardized sampling protocols are used for all field and laboratory work to facilitate spatial comparisons among sampling locations and to reduce sampling bias. The data collected through the LTRMP are subjected to a rigorous quality checking process, then warehoused at UMESC. These data and many other resources are then made electronically available to resource managers and the general public through an on-line data library. For further information on the LTRMP and access to the available data, please refer to the UMESC Web site at http://www.umesc.usgs. gov/ltrmp.html.

The LTEF was initiated in 1957 by William C. Starrett to assess fish communities in the six mainstem reaches of the Illinois River. Since that time, INHS staff have continued collecting these data at 27 fixed sites and have established a nearly continuous data set on fishery information from the Illinois River. Standardized electrofishing methods have been used throughout the project to collect fish, and coupled with this standardized sampling regime, the relatively long period of record makes this a unique data set for lotic systems. These 40+ years of information have afforded an opportunity to track general fish population trends along the entire length of the Illinois River. Some of the more interesting results include a steady decline of common carp, Cyprinus carpio, and a marked increase in Centrarchid populations (e.g., bluegill, Lepomis macrochirus, and largemouth bass, Micropterus salmoides) throughout much of the river. These trends, especially the decline in common carp abundances, have been largely attributed to improved water quality over the period of record.

Human demands on rivers will likely continue to directly and indirectly influence aquatic communities along the UMRS, and the resulting data from these two projects have proven to be, and will continue to be, invaluable in providing insight into responses of aquatic communities to biotic and abiotic change. Further, these data are also beneficial in identifying future research and management needs as restoration efforts along both the Illinois and Mississippi rivers gain momentum.

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Mark A. Pegg, Center for Aquatic Ecology

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