Channel Catfish Habitat Use in the Middle Mississippi River Andrew P Channel Catfish Habitat Use in the Middle Mississippi River Andrew P. Braun1 and Quinton E. Phelps1,2 Missouri Department of Conservation, Big Rivers and Wetlands Field Station1 Southeast Missouri State University2 INTRODUCTION RESULTS DISCUSSION The Middle Mississippi River has been subjected to river modifications such as channelization, dredging, and levees, which have reduced the availability and quality of habitats used by some river fishes (Alexander et al. 2012). Channel catfish (Ictalurus punctatus) are important ecologically because of their relatively high abundance and biomass, and their ability to occupy several niches or trophic levels (Colombo 2007). In addition, channel catfish are commercially and recreationally important to people of the Mississippi River basin (Eder 2011). Conservation of channel catfish depends on understanding habitat use, but there appears to be a lack of consensus regarding this topic. Our objective was to study channel catfish macrohabitat and mesohabitat use in the Middle Mississippi River using data from the U.S. Army Corps of Engineers’ Long-Term Resource Monitoring Program. Channel catfish SCPUE was highest in off-channel habitats with shallow water and sandy substrates. Channel catfish appear to use a range of velocities, but likely do so at different stages of their life history. Channel catfish evolved with the primeval Mississippi River, so habitats that reflect the pre-modification quality of the river are likely most important. Conservation of side channels and other shallow, sandy areas should provide suitable habitat for channel catfish in the Middle Mississippi River. Future studies could examine microhabitat use, foraging, energy conservation, or other aspects of channel catfish life history within the suitable habitats identified here to further understand the ecological requirements of this important species. Channel catfish SCPUE was lowest near main channel wing dikes, and highest in off-channel habitats (F = 9.49; df = 4, 3778; p <0.0001) METHODS Channel catfish SCPUE was highest in sandy habitats (F = 0.82; df = 3, 2984; p = 0.4831) Channel catfish were captured in the summer and fall between 1993 and 2012 during the Long-Term Resource Monitoring Program’s fish monitoring periods in the Middle Mississippi River. A variety of habitats were sampled using 15-minute daytime electrofishing runs and large and small hoop nets baited with soybean cake and set for two trap nights. Total length was recorded for all channel catfish. Water depth (m) and velocity (m/s) were measured at each set, and dominant substrate type (gravel, sand, silt, or soft particulate) and macrohabitat type (main channel border, unstructured [MCB-U], main channel border, wing dike [MCB-W], open and closed side channel [SCB-O, SCB-C], and tributary mouth [TRI] were qualitatively assessed and recorded. Catch-per-unit-effort was standardized across gear types (SCPUE; Phelps et al. 2009). Differences in SCPUE across mesohabitat and macrohabitat types were analyzed using ANOVA and Bonferroni pairwise comparisons. LITERATURE CITED Alexander, J.S., R.C. Wilson, and W.R. Green. 2012. A Brief History and Summary of the Effects of River Engineering and Dams on the Mississsippi River System and Delta. U.S. Geological Survey Circular 1375. Colombo, R.E. 2007. Demographics and the Ecological Role of Channel Catfish (Ictalurus punctatus) in Commercially Exploited and Unexploited Reaches of the Wabash River with Implications for the Flathead Catfish (Pylodictis olivaris). Doctoral Dissertation. Southern Illinois University Carbondale. Phelps, Q.E., D.P. Herzog, R.C. Brooks, V.A. Barko, D.E. Ostendorf, J.W. Ridings, S.J. Tripp, R.E. Colombo, J.E. Garvey, and R.A. Hrabik. 2009. Seasonal Comparison of Catch Rates and Size Structure Using Three Gear Types to Sample Sturgeon in the Middle Mississippi River. North American Journal of Fisheries Management 29:1487-1495. A trend for specific velocity classes is not apparent. Channel catfish appear to use a broad range of velocities (F = 2.84; df = 10, 2841; p = 0.0016) Overall, channel catfish appear to use shallow habitats more than deep habitats (F = 20.5; df = 10, 3228; p < 0.0001) ACKNOWLEDGMENTS This study was funded by the U.S. Army Corps of Engineers’ Upper Mississippi River Restoration - Environmental Management Program’s Long Term Resource Monitoring component implemented by the U.S. Geological Survey, Upper Midwest Environmental Sciences Center and carried out by the Missouri Department of Conservation.