We used an Edgetech 4125-P side-scan sonar unit operated
in high-frequency (1,250 kHz) mode, with a total swath width
of 50 m. The unit was deployed at a constant depth of approximately
1 m below the water’s surface for all systems and surveys.
Side-scan sonar data were collected and processed using
Chesapeake Technology’s SonarWiz.Map software. When a
potential sturgeon was observed on side-scan images, the target
was marked, its GPS coordinates were taken, and the target’s
body length and distance from the transect were measured.
Each river was an individual study area subdivided into 2-
km sites, for a total of 179 sites. Sites of 1 km and 4 km were
previously evaluated for their effect on occupancy, with results
bracketing the 2-km sites (Flowers and Hightower 2013). The
large amount of data collected during the surveys required
extended time for analysis. Side-scan sonar file processing
took 1–3 d/survey day, depending on how many targets needed
to be recorded.