The California Monitoring Plan (CMP) salmonid monitoring areas and associated population data are part of an ongoing effort to summarize existing and past salmonid monitoring efforts in the areas identified by Adams et al. 2011. These data are compiled and maintained by the California Department of Fish and Wildlife with the cooperation of monitoring practitioners. Updates and associated outreach are intended to occur on an annual basis. Data were created from several sources and existing datasets: some monitoring areas were accurately depicted using the USGS National Hydrography Dataset (NHD), other monitoring areas were approximated using the monitoring point location and the USGS StreamStats tool to depict the watershed area above that point. The areas are intended to represent the approximate extent of sampling within sub-basins, watershed areas, or regions. For example, the spatial extent of monitoring using a fixed count station is approximated by accounting for all anadromous fish habitat upstream of the sampling location. Therefore, the area is approximated by entering the monitoring location coordinates into the StreamStats tool. The resulting shapefile is then examined to ensure the watershed area did not include habitat above dams or barriers to migration. Areas were clipped when needed. The data user should recognize that errors may have occurred during production of this dataset, changes may have occurred to the external sources used post transfer, and for other possible reasons. The population metrics summarized in the associated tabular data may be regarded as spatially limited, temporally limited, and not considered a complete estimate for the population being described. The data user is advised to refer to the annual reports cited in the Source field from the tabular data for additional details regarding monitoring within the area spatially depicted.Abbreviation Definitions: SGS = Spawning Ground Survey, RM = River Mile, RST = Rotary Screw Trap, RKM = River Kilometer, FCS = Fixed Count Station, STH = Steelhead, CC = Coastal Chinook, DS = Downstream