Wednesday March 11, 2026
CalTrout —
Southern steelhead trout are one of the most remarkable native fish in California, an often overlooked species that inhabits the waters of our very own Southern California backyard. Known scientifically as Oncorhynchus mykiss, Southern steelhead are a distinct population of steelhead trout found in coastal watersheds from the Santa Maria River south to the U.S.–Mexico border. Unlike resident rainbow trout, steelhead are anadromous, meaning they spawn in inland freshwater streams, migrate to the ocean to grow, and return to freshwater rivers to spawn. In Southern California, their ability to survive in volatile, drought-prone watersheds with high temperatures, seasonal sand berms, and low summer flows is nothing short of extraordinary. Their persistence in some of the most urbanized waters in the state is a testament to the species’ resilience.
However, over the last century, Southern California has become one of the most densely populated regions in the country with development that can block their migration corridors and degrade the quality and expanse of their habitat. Over time, these environmental stressors can build on one another, steadily harming populations that were once stable. Today, they are found in only a fraction of their historical range, with scientists estimating their populations have declined by more than 90 percent from historical levels.