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Delta Watch

Predation

Few issues in the Delta are as clear cut as predation. Larger predator species eat smaller fish. Nonnative species pose a particularly significant predation threat in the estuary. Many of these predators were planted in the Delta for sport and recreational fishing purposes with little concern for the native species they now endanger, such as salmon, delta smelt and steelhead.

Exacerbating the problem, it has long been the State’s misguided policy to protect and maintain the populations of these predators through the use of size and bag limits. Fish stocking programs have also been utilized in the past to increase the adult populations of these voracious feeders. Many species that are nonnative to the Delta have direct or indirect impacts on native threatened species, which greatly reduces survival of native fishes.Striped bass represent a direct predatory threat to the delta smelt and salmon and yet are protected by an ongoing California Department of Fish and Game program that maintains the population at artificially high levels to the detriment of native species. Until recently, the Department restocked striped bass as part of an active population management program.

Although the California Fish and Game Commission recently refused the Department of Fish and Game’s proposal to curtail striped bass predation, efforts are still underway to address this key stressor.

Predation Facts

  • Nine-out-of-ten juvenile salmon are being killed by predators before ever reaching the Delta.
  • The National Marine Fisheries Service has stated that predation by striped bass on winter-run salmon is a “major stressor.”
  • The California Department of Fish and Game’s own experts have estimated that striped bass may consume upwards of 25-50 percent of winter- and spring-run Chinook salmon.
  • 2009 research by highly regarded fishery biologist Dr. Charles Hanson estimated that striped bass consumed 21 to 42 percent of endangered winter- and spring-run juvenile salmon, respectively. By comparison, other studies show the state and federal water projects took less than 3 percent.

Capitol Public Radio on predation

Additional Information
More information on Striped Bass

Federal Study Finds 93 Percent of Salmon Smolts on the Tuolumne River are Consumed by Striped Bass and Other Non-Native Predators

Delta Watch: It’s Time to Act on Predation

Delta Watch: Let Common Sense Prevail

Stripers or salmon - which do we want? (April 22, 2013) Redding Record Searchlight

Public to weigh in on matter of striped bass fishing rules in Sacramento-San Joaquin Delta (Nov. 1, 2011) Sacramento Bee

The Baby Salmon Feeding Frenzy in San Pablo Bay  (April 28, 2010) East Bay Express

NMFS letter to Fish and Game Commission re: striped bass (May 2010)

Congressional letter to the CA Fish & Game Commission (April 2010)

Comments before the CA Fish & Game Commission (March 2010)

Comments before the CA Fish & Game Commission (June 2008)

Letter to Governor Schwarzenegger

Coalition for a Sustainable Delta Files Lawsuit Regarding Striped Bass Sports Fishing Regulations

Fewer salmon seen in San Joaquin rivers; predators one factor (Nov. 4, 2007) Modesto Bee

Coalition for a Sustainable Delta Initiates Legal Action On Striped Bass Sports Fishing Regulations (Oct. 25, 2007)