The California Department of Fish and Game have released the findings of a study on the ancestry and genetic distinctions among populations of O. mykiss in the South-Central and Southern California steelhead Distinct Population Segments. The study focuses on 5 watersheds: the Salinas, Arroyo Grande, Santa Ynez, Ventura and Santa Clara. Samples were also analyzed from populations in the southernmost extent of the range, including Malibu and Topanga Creeks in Los Angeles County, the Santa Ana and Arroyo Trabuco basins in Orange County, and San Mateo Creek and the Sweetwater River in San Diego County.

The report is available for download in the watershed knowledge base.