Remote-sensing of Riverine Environments Utilized by Spawning Pallid Sturgeon Using a Suite of Hydroacoustic Tools and High-resolution DEMs

The pallid sturgeon (Scaphirynchus albus) inhabits sandy-bedded rivers in the Mississippi River basin including the Missouri and Lower Yellowstone Rivers and has experienced decline generally associated with the fragmentation and alteration of these river systems. Knowledge gaps in the life history of the pallid sturgeon include lack of an understanding of conditions needed for successful reproduction and recruitment. We employed hydroacoustic tools to investigate habitats utilized by spawning pallid sturgeon in the Missouri River in Missouri, Kansas, Iowa, and Nebraska, and the Yellowstone River in Montana and North Dakota USA from 2008-2013. Reproductive pallid sturgeon were tracked to suspected spawning locations by field crews using either acoustic or radio telemetry, a custom mobile mapping application, and differential global positioning systems (DGPS). Female pallid sturgeon were recaptured soon after spawning events to validate that eggs had been released. Habitats were mapped at presumed spawning and embryo incubation sites using a multibeam echosounder system (MBES), sidescan sonar, acoustic Doppler current profiler, an acoustic camera and either a real-time kinematic global positioning system (RTK GPS) or DGPS. High-resolution DEM's and velocimetric maps were gridded from at a variety of scales from 0.10 to 5 meters for characterization and visualization at spawning and presumed embryo incubation sites. Pallid sturgeon spawning sites on the Missouri River are deep (6-8 meters) and have high current velocities (>1.5 meters per second). These sites are also characterized by high turbidity and high rates of bedload sediment transport in the form of migrating sand dunes. Spawning on the channelized Lower Missouri River occurs on or adjacent to coarse angular bank revetment or bedrock. Collecting biophysical information in these environmental conditions is challenging, and there is a need to characterize the substrate and substrate condition at a scale relevant to spawning fish and developing embryos (< 1 meter). The Yellowstone River in Montana and North Dakota provides the closest analog to a reference condition for pallid sturgeon spawning habitat with a natural flow regime and relatively natural channel geomorphology. Recent documented suspected spawning on the Yellowstone River occurs in a a sand-bedded reach with patches of gravel deposits, in zones of higher velocity (1.0-1.5 meters per second) compared to the ranges of velocities available in an adjacent reach and over a range of depths (2-5 meters). Results from substrate assessments at pallid sturgeon spawning sites on the Missouri and Yellowstone Rivers may have implications for sediment and flow management as well as provide guidance for potential habitat manipulation in support of the recovery of the pallid sturgeon.