California Department of Fish and Wildlife

State of the Science Workshop on Fish Predation on Central Valley Salmonids in the Bay-Delta Watershed

Sponsors: California Department of Fish and Wildlife, Delta Science Program, NOAA's National Marine Fisheries Service

Chinook salmon in Big Chico Creek

The purpose of this workshop is to have an independent panel of experts summarize the current state of knowledge on predation of Central Valley salmonids by other fish. This information will clarify the understanding of the role of fish predation on salmonids and associated factors in salmonid life history for policy decisions focused on improving Central Valley salmonid populations. Additionally, the Panel will be asked to identify data and science gaps that exist and identify a framework for research to support future management decisions.

Workshop Details

Agenda (PDF) - Revised 7-12-13

Dates: July 22-23, 2013
Tentative Times: July 22, 9:00 AM to 6:00 PM; July 23, 1:00 PM to 4:00 PM
Location: UC Davis Conference Center

This workshop is free and open to the public. Funding for the workshop is provided by the Ecosystem Restoration Program.


State and Federal agency staffs and interested stakeholders have worked to articulate a problem statement and develop a process to assess the current state of science understanding on fish predation of Central Valley salmonids for the Bay-Delta watershed as part of a broader effort to understand the role of predation on listed species. Fish predation is a concern of many entities and the resulting workshop and state of the science synthesis will provide an objective understanding of the current knowledge and lay a foundation for future project planning and research needs. The projects that this effort will inform include the:

  1. Selection of projects for the Striped Bass Settlement
  2. Bay Delta Conservation Plan Conservation Measures
  3. Biological Opinions for the long-term operations of State and Central Valley Water Projects
  4. Fisheries Agency Coordination
  5. Delta Plan
  6. SWRCB Bay-Delta Water Quality Control Plan


  • Gary Grossman, PhD (Chair): has authored over 100 scientific publications on freshwater and marine fish community and population ecology, habitat selection and behavior, including predator effects. He is Professor of animal ecology in the Warnell School of Forestry and Natural Resources at the University of Georgia. He is on the editorial boards of Freshwater Biology and Ecology of Freshwater Fish and writes a bimonthly column for American Angler magazine.
  • Tim Essington, PhD: is a quantitative ecologist and modeler interested in food web and predator prey systems in marine, estuarine, and freshwater habitats, with application to ecosystem based management. He is an Associate Professor at the University of Washington School of Aquatic & Fishery Sciences.
  • Brett Johnson, PhD: studies the effects of nonnative fish, food web structure and trophic interactions, fisheries management, and reservoir ecology. He is Professor of Fisheries and Aquatic Sciences, Department of Fish, Wildlife and Conservation Biology, Colorado State University.
  • Jessica Miller, PhD: studies the ecology and evolution of life history diversity of marine and anadromous populations. A component of her research involves combining genetic and otolith chemical approaches to examine mixing and migration in Chinook salmon populations. She is Associate Professor in Fisheries at Oregon State University, a member of the Coastal Oregon Marine Experiment Station, based at the Hatfield Marine Science Center in Newport, Oregon.
  • Nancy Monsen, PhD: specializes in the multi-dimensional hydrodynamic modeling of the Sacramento-San Joaquin Delta. Over the last seventeen years, she has worked at the US Geological Survey (Menlo Park), ESA PWA, and Stanford University on a variety of interdisciplinary teams, to study the interaction between hydrodynamics and ecosystem dynamics. She is currently a Research Associate in Civil and Environmental Engineering Department at Stanford University.
  • Todd Pearsons, PhD: investigated and evaluated risks associated with ecological interactions among hatchery origin, non-native origin, and native origin fishes in freshwater environments. He serves as technical lead for Grant County Public Utility Districtís hatchery programs and assorted ecological issues. He is Associate Affiliate Professor at the University of Washington.

Charge to Panel

To accomplish the above stated workshop purpose, the invited Panel will review and assess the assembled bibliography that includes key predation studies in the Bay-Delta watershed; the Panel will conduct a brief presentation of their experience relevant to the goals of the workshop. Additionally, in a workshop setting, the Panel will hear presentations highlighting the current scientific understanding (knowledge and gaps) regarding fish predation on salmonids and receive public comment; the Panel will consider the questions posed below during the workshop and ask questions as appropriate of the speakers. Relevant comments made during the workshop will be addressed in the final report as well. Finally, the Panel will identify important data and science gaps and a framework for follow-up research that should be conducted in the near future.

Questions for Panel

  • What is the ecological context of predation by fish on Central Valley salmonids, and what can be learned from other systems that could inform our understanding of predation on anadromous salmonids?
  • What do the available data and analyses tell us about the rates and population level effects of fish predation on Central Valley salmonids? Specifically:
    • Are there appropriate methods for estimation of predation rates and population level effects from the existing data?
    • What biological and physical factors are likely to affect the impacts of predation on salmonids? Have these factors changed over time, and do they vary between the major basins (i.e., San Joaquin and Sacramento)? Do these factors vary among the major reaches of the system (e.g., spawning areas, riverine reaches, delta, bay, ocean)?
    • What is understood about the interactions among major factors influencing predation on salmonids (e.g., interactions among predators, hydrology and temperature, etc.)?
  • What related science is generally agreed upon; what are the key disagreements or uncertainties?
  • What future work (e.g., feasible scientific studies, modeling, and pilot experiments) should be done to address key knowledge gaps by testing clearly stated hypotheses to substantially reduce scientific uncertainties that lead to disagreement? Please provide guidance on appropriate study design and methods for estimating predation rates and population level effects.

Focal Species: Central Valley salmonids (spring-run, winter-run, fall-run, and late fall-run Chinook salmon, and Central Valley steelhead)

Geography: The focus will be on the estuarine and juvenile outmigration riverine portions of the watershed (anadromous waters of the Central Valley) with consideration of the marine and spawning areas.

Life stage(s): all (but focus is on the juvenile - fry, parr, and smolt)

Schedule for Deliverables

  • Panel report addressing questions - Sept. 2013
  • Research Strategy - Sept. 2013


Feb. - March 2013: Outreach to Stakeholders

March - May 2013: Workshop Planning

July 22 and 23, 2013: Hold Public Workshop; present panel; have presentations; take public comment

Early Sept. 2013: Post Panel Report

Contact Person

For more information, contact Carol Atkins at or (916) 445-0074.

Additionally, if you have comments or additional information to submit, please send them to Please do not send material to the Panel members. Thank you.