A Comparison of Fish Communities in Contiguous Backwater and Vegetated Impounded Areas of Pool 19, Upper Mississippi River

Lock and dam 19 in Keokuk, Iowa has impounded over 9 m of sediment since 1913, which has created a unique shallow-water ecosystem in pool 19 that is dominated by floating-leaf and submersed aquatic vegetation The importance of these post-impoundment, vegetated areas for fish is not well understood. To increase our understanding, we compared the community structure, composition, and size structure of fish between vegetated impounded areas and non-vegetated, contiguous backwaters in Pool 19.  We sampled 180 randomly stratified sites for four, 6-week periods from May 19th- Oct 31st, 2014. We fished paired sets of tandem fyke (1/4 in. diameter mesh) and mini-fyke nets (1/8 in. diameter mesh) using LTRM standardized methods. We sampled 63,503 fish representing 64 species (48,879 fishes and 50 species from impounded sites and 14,624 fishes and 55 species from contiguous backwater sites). Species composition and structure were highest in the impounded areas. These results suggest that as sediment continues to accumulate and the size of vegetation beds increases in Pool 19, the resultant aquatic vegetation and associated habitat for catastomids and cyprinids will likely expand.