Pasadena Non-Profit Spearheads the Monitoring of Rainbow Trout
The Arroyo Seco stream, a main tributary of the Los Angeles River, is impacted by passage barriers, like many of our country’s waterways. From 80-foot tall concrete dams to Arizona crossings and recreational rock piles, the streamflow is impacted, which has trickle-down effects (literally and figuratively!). What makes the Arroyo Seco stream a unique focus of conservation, is the resilient presence of the Rainbow Trout (Oncorhynchus mykiss) despite the anthropogenic barriers, unpredictable precipitation levels, and natural disasters.
After the Bobcat Fire of 2020, the California Department of Fish and Wildlife translocated 469 Rainbow Trout from the West Fork San Gabriel River to the Arroyo Seco stream to avoid destruction and degradation of their stream habitat from debris and heavy sediment loads.
Since then, Arroyo Seco Foundation (ASF), a non-profit focused on watershed health and natural resource conservation based in Pasadena, California, has been monitoring the presence and size of the trout population and water quality parameters between the barriers.
Most recently, the stream survey protocol has been upgraded to utilizing GIS in the data collection step. Arev Markarian, the Environmental Scientist leading this field work, digitized the field observations since 2020, and connected it to ESRI’s ArcGIS Field Maps to automate the data collection process in the field earlier this year.
ASF’s dedication to conservation education led them to think about ways of optimizing and publicly sharing the data, while keeping in mind the presence of fly fishing and illegal trout fishing in the Arroyo Seco.
After considering different visualization methods, Arev created the Trout and Water Quality Dynamic Dashboard (Version 1.0) with ESRI’s ArcGIS Dashboards by linking the historical observation data to the Field Map app currently used in the Arroyo Seco stream during survey trips.
In addition to automating the data collection process and lowering erroneous entries, with the Field Maps application the quantitative data is now linked to field photographs of the stream for a more comprehensive overview, along with stream discharge, habitat type, and water quality parameters.
The first version of the dashboard was released to the public in December 2024 on ASF’s website (www.arroyosecofoundation.org), after being reviewed by local and state water and conservation organizations. ASF had to walk the fine line of communicating the prevalence of the trout population in our very own Arroyo Seco to emphasize the importance of water conservation and mindful recreation practices without giving illegal fishers the exact coordinates of the observed trout.
In order to best communicate the data, Arev decided to utilize the ArcOnline Hot Spot Analysis tool on the observed trout point data to highlight the portions of the stream with the highest number of trout observations.
The trout are trapped between the barriers along the Arroyo Seco, and can’t migrate south to the ocean and become Steelhead trout, and Steelhead trout cannot migrate into the mountain streams to spawn (as seen superimposed on the hotspot clouds in the dashboard map). Until these barriers are removed, trout habitat is impacted and migration is severely limited. Reduced stream volume in segments means higher water temperature, lower caddisfly presence (main food source of the trout), and less trout survivability.
ASF continues to monitor the stream, optimize the dashboard, conduct conservation outreach and education in the community, and collaborate with local and state agencies. By highlighting the spatial prevalence of the Rainbow trout, ASF hopes to increase mindfulness during recreation, ecological restoration such as the use of native plants (over non-natives), and water conservation to ensure stream health into the future.
Arroyo Seco Foundation is grateful to the California Wildlife Conservation Board, Accelerate Resilience LA, and the Rose Foundation for their generous support of this program.
Arev Markarian is an Environmental Scientist at the Arroyo Seco Foundation based in Pasadena, CA, and can be contacted at arev@arroyosecofoundation.org.
