Pallid Sturgeon Spawning Habitat on the Lower Missouri and Yellowstone Rivers

We tracked gravid female pallid sturgeon with telemetry from 2007–2015 through migrations to spawning areas in the Lower Missouri River and from 2012–2015 in the Yellowstone River.  Spawning habitat mapping used a multibeam echosounder, acoustic Doppler current profiler, and other sonar tools.  Mapped spawning reaches were several kilometers in length and included a wide range of habitats within a bend centered on smaller spawning patches defined by telemetry locations. Spawning in the channelized Lower Missouri River has been documented in multiple reaches distributed over hundreds of kilometers on or adjacent to the thalweg on outside revetted bends in relatively deep and high-velocity conditions.   Spawning on the Yellowstone River has been documented in a single 7-km reach about 10 kilometers upstream from the confluence with the Upper Missouri River.  Yellowstone River spawning patches are primarily composed of sand dunes with small areas of gravel between the dunes.  Patch structure changes considerably over annual time scales on the Yellowstone River.  Spawning habitats on the relatively unregulated and unchannelized Yellowstone River provide a possible reference condition for pallid sturgeon spawning; habitat measurements on the Yellowstone provide information to guide design of spawning habitat restoration on the Lower Missouri River.