1300 Wild Fall River Trout Tagged for Monitoring and Genetic Analysis

History of the Wild Trout Monitoring Program:

In 2013, the Fall River Conservancy and it’s partners California Trout, the UC Davis Center for Watershed Sciences, and the California Department of Fish and Wildlife launched the Fall River Wild Trout PIT Tagging Program. To date, the team has tagged and collected genetic analysis on 1300 Fall River rainbow trout with passive integrated responders, or P.I.T. tags, that help researcher’s track the movement of fish throughout the river. 

For each fish, fork length was measured, a photograph was taken, a uniquely identifiable PIT Tag was inserted, and a small fin clip was taken for genetic analysis.  The fish are then released unharmed at the same location they were captured.

Pit River - Fall River Conservancy
Photo Credit: Val Atkinson

Wild Trout Monitoring Program Highlights to Date:

  • Tagged, measured and taken genetic samples of 1300 Fall River rainbow trout
  • In the latest round of tagging, researchers “recaptured” four already tagged fish and learned that Fall River trout grow extremely fast: a 2013 eight inch trout almost doubled in size in just over a year!
  • For each fish, UC Davis researchers isolated DNA from its fin clip and then used cutting-edge DNA sequencing technology to decode its genetic information
  • Built upon the important conservation relationship with CalTrout, UC Davis Center for Watershed Sciences, and the California Department of Fish and Wildlife

Early Genetic Research Findings:

  • The most obvious and striking result from our initial genetic analysis is that the Fall River contains two very genetically distinct populations of rainbow trout.
Fall River Trout
Photo Credit: Val Atkinson
  • These races essentially behave as independent populations with very little genetic exchange.
  • By cross referencing the genetics with  movement and collection location data, we determined that one population corresponds to fish that reproduce in Bear Creek and the other is fish that spawn within the spring-fed system.

 Another interesting result is that these two populations are not only genetically differentiated, but the genetic patterns demonstrate they are also adaptively differentiated with distinct growth rates:

  • Fish from the Bear Creek population contain gene variants that will make them grow faster than the spring-fed population. This is likely necessary to compensate for the colder water temperatures experienced by Bear Creek fish early in their life.
Boating on Fall River
Photo Credit: Val Atkinson

Wild Trout Monitoring Program Moving Forward:

These results are only the tip of the iceberg as far as what will be unveiled as our genetic data collection and analysis are expended. The Fall River Conservancy, and it’s partners, are committed to ensuring that important research like this continues on the Fall River so that we can better understand the ecological issues with real science findings. To ensure this happens, the Fall River Conservancy has secured funding from the National Fish and Wildlife Foundation to continue this important work in the next couple years. Stay tuned for future FRC updates to stay abreast as this ground-breaking research project unfolds.

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