July 30, 2015
During the last two weeks of June, USGS habitat crews surveyed the pallid sturgeon spawning reach of the Lower Yellowstone River near Fairview, North Dakota. Using a compact multibeam sonar echosounder system with an inertial motion unit and real time kinematic positioning global positioning system (RTK GPS) mounted on a jet boat (figure 1), crews conducted high-resolution surveys and mapped features of the river bed in pallid sturgeon spawning patches (figure 2). Multibeam sonar has been used in recent years to understand pallid sturgeon spawning habitats on the Lower Missouri but these efforts were the first to do so on the much shallower Yellowstone River.
Multibeam sonar maps the river bottom in great detail with a “sweep” or ping of soundings taken at up to 40 times per second. This generates a very dense cloud of points which allows scientists to generate high-resolution maps of the bottom of the river and visualize features such as sand dunes, submerged trees, and scour holes (figure 3). By conducting multiple passes with the sonar throughout the day, sand dune movement can be mapped to calculate the rate of sand dune migration. This information can be used to advance understanding of how spawning habitat may change while eggs are incubating in the substrate.