Cooperative Research Units
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Linking predation mortality to predator density and survival for out-migrating Chinook Salmon and steelhead in the lower San Joaquin and South Delta


January 2017 - December 2018


Abundance data for fish predators is in the Delta is lacking, and has been identified as a primary research need in the Delta. The limited abundance data currently available for predators in the Delta cover relatively few locations and periods during the year, and fishery independent population estimates are unavailable. Both native and non-native species of predator fishes inhabit the South Delta and feed on migrating smolts and there is likely significant annual and seasonal variation in the presence of absence of individual predators. Predators are likely to exhibit positive selectivity for salmonid species because they are highly caloric, are likely naive to invasive predators and have no physical defense structures; therefore are easily eaten and handled. Our ability to make qualitative inferences about the scale and effects of fish predation on the salmonid population are greatly hindered by this lack of information. Through a combination of paired electrofishing sampling and results from acoustic surveys conducted using Dual-frequency identification sonar (DIDSON), we will be able to quantify the abundance of potential predatory fish throughout our study region.

Research Products and Activities


  • Loomis C. and Henderson M. 2018. Estimating predator fish density and abundance in the Sacramento-San Joaquin Delta using DIDSON Acoustic cameras. 36th annual salmonid restoration conference. Fortuna, CA. April 11-14, 2018.
  • Loomis C. and Henderson M., 2018. Estimating Delta predatory fish abundance with DIDSON acoustic cameras. 10th biennial Bay-Delta Science Conference, Sacramento, CA. September 10-12, 2018.

Current Staff

Federal Staff: 99

Masters Students: 225

Phd Students: 143

Post Docs: 53

University Staff: 247

5 Year Summary

Students graduated: 658

Scientific Publications: 1872

Presentations: 4186



Funding Agencies

  • California Department of Fish and Wildlife


Cooperative Research Units Program Headquarters Cooperators

  1. U.S. Geological Survey