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We examined the use of "edge of flood" habitats by larval silver carp during the extensive flooding that occurred in Pool 26 of the Upper Mississippi River near Alton, IL, USA and St. Louis, MO, USA during the summer of 2015. We captured over 12,700 individual fishes including eight taxa, over 12,000 of which (> 95%) were larval silver carp between 5 and 21 mm standard length. Peak catch rates occurred near the confluence of the Illinois and Mississippi rivers. These findings suggest that larval silver carp have an affinity for edge of the flood habitat and further study is needed to better understand how this affects the dynamics of this invasive species in the Mississippi River. The high catch rates observed at the confluence of the Illinois and Mississippi rivers suggests that the Illinois River is an important source of larval silver carp to the Upper Mississippi River.

Abstract Sportfish species, specifically Yellow Bass Morone mississippiensis, White Bass Morone chrysops, Largemouth Bass Micropterus salmoides, Bluegill Lepomis macrochirus, Black Crappie Pomoxis nigromaculatus, and White Crappie P. annularis, often drive economically valuable fisheries in large river systems, including the Upper Mississippi River System (UMRS).  Within the Illinois River, part of the UMRS, these species are routinely sampled by an ongoing long-term fisheries monitoring program.  Through this program, we investigated long-term trends (1993-2017) in catch rates and relative weights and quantified demographic rates from 2012-2016. We found all six species, with the exception of Yellow Bass, to have declining catch rates with this decline being most stark in larger, older fishes.  Population demographics for Yellow Bass, White Bass, Bluegill, and Black Crappie suggest populations are dominated by younger individuals, with only Black Crappie regularly living to age 3 and older, which may be driving population declines.  There are many environmental stressors acting on the Illinois River that could be contributing to the lack of older and larger fishes, including, but not limited to, navigation efforts, altered hydrology, pollution, sedimentation, lack of overwintering habitat, and introduction of invasive species.  Results of this study demonstrate that additional research to understand mechanisms driving reduced abundance and stunted age structure are needed to identify effective management actions that would benefit populations of recreationally valuable sportfish species.