By John Goraj
Myself, along with three other volunteers, began the scout at the Altadena Crest Trailhead in Altadena. We hiked for about two and a half miles on the Gabrieleno Trail along the Arroyo Seco to Gould Mesa Trail Camp, eventually turning around somewhere between Gould Mesa and Paul Little Picnic Area. The Arroyo is beautiful right now and as always, a very thriving ecosystem. We saw several California newts, who are mating right now and mountain yellow-legged frogs.
We stopped several times along the way making several notes about trout habitat and riverine conditions. We saw several things that made me confident of the existence of rainbow trout in the Arroyo. Here are some of the major habitat features that we discovered in several key habitat categories.
This central section of the stream currently possesses all of the necessary habitat requirements needed for native southern California trout to thrive; cool and clear water, stable undercut banks, clean gravel beds with little to no silt, overhanging vegetation, structural/habitat diversity and the food that trout eat.
The stream is flowing well about 5-10 cfs and the water temperature is cool. The banks along this section of the stream are undercut creating sufficient pool depth for trout to live in during the drier summer months.
Additionally, the roots of white alder trees which grow abundantly along the stream provide strong support along the banks. The gravel beds are clean and soft creating high quality habitat for trout to possibly spawn in the future. Canopy cover above the stream (overhanging vegetation) was almost always 50-to-75 percent, which keeps dissolved oxygen adequately high for native trout to thrive.
Lastly, many of the key components of trout dietary needs were present as well. These include terrestrial insects, spiders, midges, dragonflies and water boatman bugs.
Perhaps the most promising feature was the discovery of several two-to-four-foot-deep pools created by in-stream structural diversity, such as boulders and large woody debris. These pools are essential for trout survival and illustrate the important function that downed logs and boulders play in providing high quality for trout.
I will keep you all updated on the next “Trout Scout” and any possible trout sightings!
John Goraj is the Native Trout Program Manager at the Arroyo Seco Foundation.