Wild Trout Monitoring Program Results

History of the Wild Trout Monitoring Program:

In 2013, the Fall River Conservancy, 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 1561 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 where they were captured.

Now that we have tagged over 1500 fish, there is some early data to look at:

Now that we have accomplished several tagging “events” we occasionally recapture fish that already have tags in them. This is particularly exciting because it gives us insight into the growth rates of that particular fish, and for Fall River trout in general. Slides 1 and 2 below  summarize the fork lengths for all wild rainbow trout that been tagged to date in slide 1, and the growth rates of the “recaptured” fish in slide 2. One thing we know for sure is that Fall River trout grow extremely fast: a 2013 eight inch trout almost doubled in size in just over a year!

Another exciting part of this research is learning about how trout move through-out the springs and rivers that make up the Fall River Watershed. Slide 3 below shows where current PIT tagging arrays exist on the Fall River. These arrays are what detect the unique PIT tags within the tagged fish as they swim by.

As of October, 2015, 188 (12%) of the 1561 tagged fish have been detected at least once at the 1000 Springs, Bear Creek, or Graybarn PIT arrays since the arrays were installed in February, 2014. This is shown in slide 4.

The more that the UC Davis Center for Watershed Sciences gets into this data, the more there is to learn. Each time one of the arrays picks up a unique fish ID as it swings by, it helps to identify patterns in individual fish behavior (such as redd building or staging before Beak Creek migration) and/or group social behavior (such as spawning aggregations). An example of this is depicted in slides 5 and 6. 

Wild Trout Monitoring Program Moving Forward

These results are only the tip of the iceburg as far as what will be unveiled as our data collection and analysis are expended. The Fall River Conservancy and our important partners CalTrout, UC Davis and CDFW 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, we need your continued support to ensure we make this program happen in 2016 and beyond.

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