Southern California Steelhead trout (Oncoryhnchus mykiss) range from Santa Barbara County south to the U.S.-Mexico border. The species has a unique life history, an adaptation to a semi-arid climate, and are geographically located at the periphery of the species' Pacific range. Like all steelhead trout, adult steelhead trout spend their life in the open ocean before swimming up stream to spawn. Juvenile trout usually stay in the streams for a couple of years before heading out to the open ocean where they complete their growth to an adult.
Because southern California streams are drier than those found in the north, streams are inaccessible from the ocean for most of the year and only become accessible during significant rain events. For some streams, this opportunity might not occur for several years. Steelhead trout have adapted to these drier conditions by spending less time in the streams, and use the opportunity when streams are accessible to swim up stream to spawn or out to the open ocean.
For the steelhead eggs to develop, grow and eventually make their way to the ocean themselves it is most important that streams have enough food, cover and water the rest of the year when it is hot and dry. Unfortunately, existing land uses such as road crossings, flood control channels, culverts and small check dams have prevented trout from migrating into and out of many of the streams in southern California. In addition, the introduction of non-native competitors, such as crayfish and mosquito fish, as well as an increase in run-off from urban development and agriculture has lead to a degredation of the spawning habitat.