Large mouth and striped bass taken from Clifton Ct Forebay
Clifton Court Forebay is a 2,000-acre lake that feeds Delta water to the State Water
Project Banks pumping plant. It has long been known as a major loss location for juvenile salmon smolts from the San Joaquin and Sacramento Rivers. A number of studies have confirmed that survival of San Joaquin smolts through the Delta is between two and five percent. Because of this, there is virtually no current contribution of San Joaquin salmon to the ocean fishery in most years. Clifton Court losses are likely the number one contributor to these failures.
In 2013, the Department of Water Resources (DWR) completed a study of predation losses in Clifton Court using PIT tagged salmon smolts. The conclusion of the study was that 81 percent of the smolts were lost to predation before they got to the louvers at the pumps. Further studies revealed that Clifton Court is packed with predatory striped bass, catfish and black bass.
DWR did a three year test electro shocking and predator removal and relocation program in the forebay which removed the predators to Bethany Reservoir near Byron. With estimates of up to 200,000 striped bass in Clifton Court, it appears this approach can’t be scaled up to where it would have an impact.
A 1993 test where a commercial fisherman seine netted Clifton Court removed more than 32,000 predators including 29,000 striped bass. To date this appears to be the most promising approach short of redesigning and building a new water intake structure.
In 2009, the National Marine Fisheries Service released a salmon biological opinion that included a requirement that by 2011 a project must be scoped to reduce the pre-screen predation at Clifton Court to 40 percent of what it was in 2009. The project was to be completed by 2014, which didn’t happen. NMFS also required that predation be reduced at the salvage discharge facilities by 50 percent (GGSA project D.17). That measure also required an evaluation of net pens as alternate to pipe discharges. That evaluation has not been completed. Both the Clifton Court and the salvage projects are badly needed for the benefit of the salmon.