Physical Factors Affecting Drift of Pallid Sturgeon Free Embryos in the Missouri River Basin

Substantial geomorphic and hydraulic alterations throughout the Missouri River Basin have fundamentally transformed the availability, distribution, and quality of aquatic habitat for Scaphirhychus albus (pallid sturgeon). Channel modifications, flow regulation, and establishment of a self-dredging navigation channel in the Lower Missouri River alter flow depths and velocity, and these altered physical processes in turn change drift dynamics for free-embryo dispersal. Substantial research and conservation efforts have focused on drift dynamics because of high mortality associated with this life stage. We synthesize findings resulting from analyses of 1D advection dispersion models, extensive hydroacoustic field data, 2D hydrodynamic models, and preliminary experimental data in order to evaluate drift dynamics in Yellowstone, Upper Missouri, and Lower Missouri Rivers. Together, these data illustrate the differences in drift dynamics in channelized, restored, and unaltered reaches of the Missouri River basin. We explore how channel modifications and flow regulation influence the hydraulic environment free embryos encounter while drifting and how these physical processes may affect the transition from drifting free embryo to exogenously feeding larvae.