The aim of the Federal Endangered Species Act (ESA) is to recover species that would otherwise go extinct, and to this end it requires the Federal government to prepare recovery plans. A recovery plan outlines a strategy for lowering extinction risk to an acceptable level, and has two components: a technical part and a policy part. The technical part evaluates information on the species itself, and especially the changes in abundance, distribution, habitat condition, etc., that would reduce the extinction risk. The policy part determines which of the risk-reducing changes are desirable and feasible, outlines the steps necessary to bring them about, and estimates their cost.

For West Coast salmon and steelhead, these two parts are formally labeled “Phase I” technical recovery and “Phase II” implementation by the National Marine Fisheries Service. This report concerns Phase I, and applies a formal evaluation framework developed elsewhere (McElhaney et al. 2000, Bjorkstedt et al. 2005) to the problem of delineating Oncorhynchus mykiss populations in the South-Central/Southern California Coast recovery domain. These populations inhabit the set of coastal river basins encompassed by the Pajaro basin in the north and the Tijuana basin in the south, hereafter referred to as the study area.