Acoustic Telemetry Methods for Evaluating the Efficiency of Protecting Salmonid Juveniles with a Non-Physical Barrier in California's Central Valley

Populations of anadromous salmonids in the Sacramento-San Joaquin Delta of California continue to decline. Survival estimates of migrating juveniles have shown that some routes through the delta are more favorable for survival than others. In an effort to increase the proportion of downstream migrating juveniles using more favorable routes, non-physical barriers have been installed at channel junctions to direct juveniles to more favorable channels. To evaluate the effectiveness of these barriers, high resolution acoustic tag arrays were installed at the junctions to develop tracks of acoustically tagged smolts. These tracks helped determine if the fish were actually responding to the barrier, or were simply guided by flow. Concurrently, Acoustic Doppler Current Profiler (ADCP) instruments monitored water velocities within the array. This paper describes the methods and techniques used to develop high resolution tracks of acoustically tagged fish. Combining fish movement data with flow data was a powerful tool for determining the effectiveness of non-physical barriers at directing fish into favorable migration routes.