Assessment of Floodplain Benthic Invertebrates and Invertivores on the Missouri River

Floodplain connectivity is important to the life history of aquatic organisms in large river systems.  Anthropogenic alterations regulating the Missouri River have limited connectivity and may be negatively affecting native fauna.  We assessed benthic invertebrates and benthic invertivorous fishes at three Missouri River floodplain sites (Baltimore, Dalbey, and Overton) as part of a larger floodplain monitoring study during the high water event of 2011.  Dipterans dominated most samples and oligocheats and trichopterans were occasionally abundant.  Benthic invertebrate species diversity peaked approximately three weeks post-inundation, and catch rates were initially high at Baltimore and Dalbey but declined as high water persisted.  Similar trends in catch rates were evident for benthic invertivores.  Species-specific differences were rare among invertivores within each sampling trip; thus, catch rates were pooled.  Invertivore catch rates were similar among sites, but differed among sampling trips with the highest catch rates observed shortly after inundation.  Multidimensional scaling also showed relatively high dissimilarity of catch rates between early and late sampling trips.  Linear regression analysis suggested invertebrate catch rates can explain a large amount of variation in invertivore catch rates.  Our results suggest that short-term inundation may be more beneficial to benthic invertivores and their prey than prolonged inundation.