Salmon Evolutionarily Significant Units (ESUs) - West Coast of USA

This dataset includes the boundaries evolutionarily significant units (ESUs) of salmon on the West Coast of the United States of America. An evolutionarily significant unit, or ESU, of Pacific salmon is considered to be a "distinct population segment" and thus a "species" under the Endangered Species Act. Chinook salmon, Chum salmon, Coho salmon, Pink salmon, Sockeye salmon, and steelhead are all included in the dataset.

ESU boundaries were compiled by the GIS group at the Bonneville Power Administration from various sources based on written descriptions in NOAA Fisheries Service status reviews (available upon request) and mapping provided by the Fisheries Service. Initial boundaries were derived from USGS 1:250,000 scale hydrological unit boundaries. Boundaries were modified based on migration blockages and known fish distribution. Drainage basin delineation from blockages was based on 1:100,000 stream hydrography and/or available digital topography (1:250,000).

ESU polygons depict major basins within the current known range of each ESU. Species do not necessarily inhabit all drainages or river reaches depicted. More detailed information on species distribution within each ESU is available from NOAA and other federal, state and tribal resources.

Updated July 27, 2006.

Please refer to the Listing Status Snapshot (PDF 50KB) to confirm the ESA listing status of each species.

No liability is assumed for the accuracy or completeness of the ESU information.

More information can be found at the NOAA National Marine Fisheries Service, Northwest Regional Office Salmon Populations website.