The Current Magazine Spring 2015 - Page 33

History of the Wild Trout Monitoring Program

In 2013, California Trout and its partners the Fall River Conservancy, 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 wild trout throughout the river.

For each fish, we measure fork length, take photographs, insert a uniquely identifiable PIT Tag, and take a small fin clip for genetic analysis in a UC Davis laboratory. We then release the fish unharmed at the same location of their capture. This research will allow us to assess scientifically the current health of the fishery, establish a baseline, and identify threats to Fall River native trout over time.

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.

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. 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.

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. California Trout and the Fall River Conservancy 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, California Trout has secured funding from the National Fish and Wildlife Foundation to continue this important work in the next couple years.