This report presents a summary of data collected during segment 06 (2019-2020) of the Upper Mississippi River fish population monitoring and sport fish assessment in west-central Illinois, an annual survey by staff of the Illinois Natural History Survey, with funds administered by the U.S. Fish and Wildlife Service and the Illinois Department of Natural Resources. Sampling for the program was conducted on 6 navigational pools of the Upper Mississippi River. All fishes collected were accurately identified, counted, measured, and weighed. The catch rates of several key species were calculated as the number of individuals collected per hour (CPUE ± standard error). Proportional size distribution (PSD) was also calculated for several key species. Catch rates and species varied among all sampling locations and sampling periods. Emerald Shiner and Gizzard Shad comprised most the individuals caught, and Common Carp and Smallmouth Buffalo accounted for the greatest proportion of the biomass collected.
Sportfish
Catch rates and sizes of popular sportfish species varied greatly among the navigation pools sampled during 2019. Bluegill and Channel Catfish were the most-abundantly collected sportfish species in nearly all areas along the Upper Mississippi River, although Largemouth Bass and Smallmouth Bass also appear to have robust populations. The slow but steady increase in White Bass CPUE since 2012 may warrant further investigation. Our long-term datasets allow us to observe substantial annual variations in the relative abundance and size distribution of many sportfish species, like Smallmouth Bass and White Bass. These observations could serve as a catalyst for future research investigating the effects environmental changes and management policies on the sustainability of Illinois’ sportfish populations.
Invasive Species
Although the main focus of the F-193-R project is to conduct monitoring to improve our understanding of population dynamics, life histories, and habitat requirements of sportfishes, the program’s sampling strategies are also useful for documenting trends in the relative abundance of non-native species occupying Illinois’ large river ecosystems. Our surveys suggest Common Carp populations are declining across the region since 2009, which may be the harbinger of good things to come for native fish populations that have been negatively affected by Common Carp. Alternatively, Silver Carp populations (below L&D 19) appear to be increasing since 2012, which may counteract any benefits native fish populations may have gained as a consequence of declining Common Carp populations. We advise that researchers be aware that our sampling protocols (e.g., restriction to main-channel habitats) may limit our probability of encountering the greatest densities of invasive species.Illinois Department of Natural Resources, Division of FIsheriesU.S. Fish and Wildlife Service Project F-193-R Segment 06unpublishednot peer reviewedOpe
