Imaging Sonar data collected using ARIS Explorer 1800 sonar using 1.8 MHz frequency. The sonar data were collected in an experimental pond (width: 6.5 m, length: 46 m, depth: 0.8 m). The velocity regime of the experimental pond was slow and relatively constant (0.08 – 0.14 m/s: measured using a SonTek FlowTracker). An imaging sonar (ARIS Explorer 1800, Sound Metrics Corp.; www.soundmetrics.com) was set facing across the pond and perpendicular to the current. The transducer was mounted 0.05 m below the water surface. Three fish species were in the pond at separate times: Atlantic salmon (number of fish in the pond n=43), striped bass (n=100), and American shad (n=13). More information in