Stillwater Sciences was contracted by the California State Coastal Conservancy toestimate the current spatial extent of selected "focal" species’ habitat in the Santa Clara River mainstem (mouth to Ventura/Los Angeles County line) and major tributaries (Piru, Sespe, and Santa Paula creeks). Focal species were selected from a list of candidate species that currently occur or historically occurred along the lower Santa Clara River, based on their status under state and federal Endangered Species Acts, the occurrence of suitable habitat within the vicinity of the project area, and the ecological niche they represent. They cover a range of aquatic, riparian, and upland habitat requirements and represent various taxonomic groups and guilds within the river corridor ecosystem. A few of the selected species no longer occur in the project area, but were included because they might recolonize or be re-introduced if habitat is restored. For each focal species, the different life history stages that occur in the Santa Clara River were identifed, as well as the habitats used by each of those life history stages, the ecological processes that create and maintain those habitats, and the management actions that influence those ecological processes and habitat conditions. The spatial extent of potential habitat was estimated using recent field studies, aerial photographic interpretation of riparian vegetation and channel planform evolution, reviews of scientific literature, and interviews with local experts. An analysis of the life history and habitat requirements of each focal species was used to identify the relative importance of various habitat features along the lower Santa Clara and to evaluate the degree to which restoration strategies may benefit these individual species, many of which have declined and may require habitat restoration to persist in the area.