THE LONG-TERM ILLINOIS, MISSISSIPPI, OHIO, AND WABASH RIVERS FISH POPULATION MONITORING PROGRAM 2012

This report presents a summary of those data collected during segment 24 (2012-13) of the Long-term Illinois, Mississippi, Ohio, and Wabash Rivers Fish Population Monitoring Program (LTEF), an annual survey executed by members 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 LTEF program was conducted in twenty study areas: six reaches of the Illinois River Waterway, six segments or pools of the Mississippi River, four segments or pools of the Ohio River, and five segments of the Wabash River. Six reaches of the Illinois River Waterway were sampled from Aug-Oct 2012 using boat-mounted AC electrofishing arrays at 28 fixed sites. Sampling was conducted during June-October2012in five reaches of the Illinois River Waterway, six segments or pools of the Mississippi River, four segments or pools of the Ohio River, and five segments of the Wabash Riverusing boat-mounted pulsed DC electrofishing gears. Gill net collections were conducted in two sections of the Mississippi River during fall 2012 and spring 2013. In all segments of the LTEF program, all fish species collected were accurately identified, tallied, measured, and weighed. The capture rates of each species were calculated as the number of individuals collected per hour (CPUEN) and the weight of a given species collected per hour (CPUEW). Samples collected using AC electrofishing were characterized by high species richness and relatively high capture rates of notable fish species (e.g. bluegill, smallmouth bass, smallmouth buffalo, silver carp, and common carp). Over 39,000 fishes were captured in the larger-scale pulsed DC electrofishing survey, although capture rates and species richness varied greatly among all sampling locations and time periods. Emerald shiners and gizzard shad comprised the majority of the individuals captured, while silver carp and common carp accounted for the greatest proportion of the biomass collected in all segments of the DC electrofishing surveys. Both shovelnose sturgeon and blue catfish were the two species most commonly encountered in the gill net surveys. An analysis of gill netting data suggests that sampling at randomly selected wing-dam habitats may be the most effective strategy for long-term monitoring of shovelnose sturgeon and blue catfish abundances in future years. While the factors controlling the annual variations in the relative abundances of fishes in Midwestern Rivers may be difficult to measure, our ability to detect and possibly explain such changes is dependent upon the execution of well-designed fisheries surveys. The operation and maintenance of the LTEF program and the data it generates can contribute to more complex and nuanced understandings that can, in turn, aid in the development of more effective and sustainable management policies for the rivers of Illinois.