As part of a release site predation study, the California Department of Water Resources (DWR) took this DIDSON video of “salvaged” fish being released in the Delta. Salvaged fish are trucked to Delta release sites from the John E. Skinner Delta Fish Protective Facility, which removes fish before they enter the Harvey O. Banks Pumping Plant and become trapped and lost in the California Aqueduct. During this particular release event in August 2007, over 31,000 fish (mostly threadfin shad, striped bass, and American shad) are seen being released through a pipe from a hauling truck. In this video, some predator fish can initially be seen milling around the exit of the release pipe. Then, as salvaged fish are flushed from the pipe into the receiving waters, a cloud of turbulent water containing salvaged fish is seen. And, in a matter of seconds, predatory fish respond by attacking and eating the fish that are disoriented by their abrupt entry into the Delta.
DWR has utilized dual frequency identification sonar (DIDSON) technology to capture video of predator abundance and behavior associated with fish releases from August 2007 through April 2008.