Invasive Brown Trout Population Assessment and Suppression Feasibility Pilot Study Phase 2 FY2014

Salmonid Research, Monitoring, and Evaluation (RM&E)

Monitoring Research
Recovery DomainsN CA - S Oregon
Start Date09/30/2015
End Date09/30/2016
Last Edited05/08/2024
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This project involved a second round of Brown Trout collection through a variety of methods including electrofishing, angling, and capture at fish sampling weirs to provide information on trout population size, distribution, age, and diet. Captured brown trout were sampled for stomach contents, tissue samples and scales were taken for analysis to assess diet and age. In addition to data collection scales were used to calculate growth and mortality rates, and mark recapture rates were used to establish population estimates for both years of sampling. Results from this assessment will be used to illuminate the magnitude of the problem and capture success rates will inform suppression feasibility while implementing a one-time suppression treatment via fish collections. This project was conducted in close coordination with NOAA, USFWS, CDFW, the Yurok Tribe and Humboldt State University. This project was conducted by Justin Alvarez, a tribal member and employee of the Hoopa Valley Tribal Fisheries Department, and Dr. Darren Ward at Humboldt State University, as part of a masters thesis project by Mr. Alvarez.

Project Benefit    

As the study progresses we are finding that Brown Trout are consuming many Coho salmon especially age 1+ individuals. The timing of this years electrofishing efforts will provide more insight into Brown Trout diets when hatchery fish are not as available. This will allow a more clear picture as to the proportion of the various prey Brown Trout are consuming. An additional benefit is a better understanding of what time of year is best for a removal effort in any suppression actions. A more efficient removal will provide the largest benefit to ESA listed salmon with the least impact to the native fishes of the Trinity River. Activities and methods are to collect biological data on brown trout and analyze results to recommend management. A complete list of methods was provided to NOAA Fisheries for review.


Metric Completed Originally
Research and Monitoring
  Stream Miles Monitored 42.00 42.00

Funding Details

Report Total:$67,240

Project Map


Trinity River    

  • Worksite Identifier: Trinity River
  • Start Date: 07/01/2014
  • End Date: 02/29/2016
Area Description
Upper Trinity River

Location Information

  • Basin: Klamath (180102)
  • Subbasin:
  • Watershed: 1801021107
  • Subwatershed:
  • State: California
  • Recovery Domain: N CA - S Oregon
  • Latitude: 40.714489175
  • Longitude: -122.980540877


  • Southern Oregon/Northern California Coast Coho Salmon ESU




  • E.0 Salmonid Research, Monitoring, and Evaluation (RM&E)Y (Y/N)
    •      . . E.0.a RM&E Funding 67,240.00
    •      . . E.0.b
      Complement habitat restoration project
      Trinity River Restoration Program
    •      . . E.0.c
      Project identified in a plan or watershed assessment.
      SONCC Coho Restoration Plan
    •      . . E.0.d.1 Number of Cooperating Organizations 9
    •      . . E.0.d.2
      Name Of Cooperating Organizations.
      Yurok Tribe, US Forest Service, NOAA Fisheries, Bureau of Reclamation, Trinity County, Hoopa Tribe, US Fish and Wildlife Service, California Department of Fish and Wildlife, California Department of Water Resources
    •      . . E.0.e.1 Number of reports prepared 0
    •      . . E.0.e.2
      Name Of Report
      None - to be published at end of study (in 2017)
    •      . . E.1 MonitoringY (Y/N)
      •      . . . . E.1.a Monitoring funding 37,240.00
      •      . . . . E.1.b.1 Stream Miles Monitored 42.00
      •      . . . . E.1.b.2 Acres of Watershed Area Monitored 18,560,000.0
      •      . . . . E.1.b.3 Square miles of water monitored29000 (Square miles)
      •      . . . . E.1.c.18 Predator/competitor monitoringY (Y/N)
        •      . . . . . . E.1.c.18.a # miles (to nearest 0.01 mile) of stream or streambank monitored 40.00
        •      . . . . . . E.1.c.18.c # acres (to nearest 0.1 acre) monitored 654.3
        •      . . . . E.1.d
          Name Of Comprehensive Monitoring Strategy/Program
      •      . . E.2 ResearchY (Y/N)
        •      . . . . E.2.a Research Funding 30,000.00
        •      . . . . E.2.b.1 Modeling and data analysisY (Y/N)
          •      . . . . . . E.2.b.1.a
            Key issues addressed by modeling and data analysis research
            This is a study of impacts of non-native predator Salmo trutta on SONCC coho salmon as well as other native anadromous fishes of the Trinity River. Study develops data on feeding behaviors of Salmo trutta, population size and population age structure as input to bioenergetic modeling to assess likelihood of substantial impacts to native fishes at the population level.