Comparison of two hydroacoustic technologies to evaluate migrating fish behavior at a large hydropower project

Split-beam hydroacoustics and acoustic tag technologies independently evaluated the downstream migrating salmonid behavior approaching the Rocky Reach Dam Juvenile Fish Bypass system in the spring of 2009.  Split-beam transducers mounted in the East and West entrances to the bypass identified diel passage behavior of salmon smolts.  Concurrently, signals from the acoustically tagged juvenile sockeye salmon (Oncorhynchus nerka) provided route specific passage information from hydrophones deployed around the forebay and bypass entrances.  Selective use of the East entrance to the bypass was revealed by both the active (71.9%) and the passive (70.2%) hydroacoustic methodologies.  The corroboration of the data from these two technologies within the infrastructure of a dam provides new insight into the approach behavior and horizontal distribution of migrating juvenile salmon.