Influence of Flow Regime on Condition of Blue Suckers in the Lower Missouri River

Flow regime is an important factor that shapes the life history and drives the distribution and abundance of riverine species.  High and low flow events provide differing ecological benefits and environmental stressors to biota in a large river system.  Although large upstream dams have regulated much of the Missouri River since 1960, the diverse native fauna in the lower Missouri River (LMR) still experience a wide range of flow variation.  Blue sucker (Cycleptus elongatus) is intolerant of habitat degradation, making it a likely indicator of ecosystem integrity.  We evaluated condition (relative weight; W_r) of blue sucker in the lower Missouri River at differing flow types (high, intermediate and low) between 2003-2011 using a two-way ANOVA.  Preliminary results indicate blue suckers had the highest mean W_r (89.6) during intermediate flow years.  Mean  W_r of blue suckers during low and high flow years were similar (86.8 and 85.1, respectively), and were 3-5% lower than in high flow years.  Our results indicate that intermediate flow types may beget environmental conditions supporting higher  blue sucker condition in the LMR.  Years with intermediate flow in the contemporary LMR most mimicked ecologically relevant components of a natural flow regime.