Biological Responses of Large-River Fishes to Hydrological Conditions on the Missouri River

Fishes of the Missouri River historically adapted to its diverse habitats and fluctuating hydrograph. Construction of six main stem dams for flood control and channelization for navigation resulted in widespread habitat homogenization. These major river alterations have adversely affected the population dynamics and reproduction success. Therefore, our objective was to determine if specific hydrological conditions were responsible for biological responses from selected native riverine fishes.  A long term data set was used to examine changes in Shovelnose Sturgeon Scaphirhynchus platorynchus and Blue Sucker Cycleptus elongates condition and recruitment from 2003 to 2014. Condition of Shovelnose Sturgeon and Blue Suckers was significantly higher during the 2011 flood but quickly returned to pre-flood levels in the following years. Recruitment patterns for both Shovelnose Sturgeon and Blue Suckers followed a similar trend, with higher peaks occurring during flood event as well as during the low flow periods in 2006 and 2007. These results suggest that low flow periods and high flow periods may provide important habitat heterogeneity. Efforts to relate biological responses to environmental conditions can provide guidance for water management in the Missouri River and other regulated North American rivers.