Bird predation

As noted in a previous post feeding frenzy the Department of Water Resources (DWR) conducted a predation study at release locations for the State Water Project (SWP) and Central Valley Project (CVP) fish salvage facilities. As part of their study, DWR utilized dual frequency identification sonar (DIDSON) technology to capture video of predator abundance and behavior associated with fish releases.

Avian predation was also considered in the DWR predation study. Researchers observed cormorants diving at the SWP Horseshoe Bend release site and this DIDSON video clip clearly shows cormorants successfully feeding on salvaged fish as they exit the release pipe.

Cormorants are common piscivorous birds, well suited for rapid swimming in pursuit of fish. They have short powerful legs with all four toes webbed and a slender beak hooked at the tip for grabbing and holding fish. In fact, they are so good at catching fish Chinese and Japanese fisherman have been using them for the past 1,300 years to harvest fish.

The final report is due to be released in the winter 2010. For more information, visit the project website.

Video source: DWR