Salmon Stock Status Mapping

To assemble this bioregional synthesis of the status of North American Pacific salmon stocks we gathered peer-reviewed or scientifically credible information from scientific papers, public agencies and non-profit organizations and compiled these data in a Geographic Information System (GIS).

As the basic unit of scale, we adopted what hydrologists refer to as fourth-field watersheds. Large watersheds are broken into tributaries, and small adjoining basins are considered as a whole. For some coastal areas where a smaller scale was required to distinguish between differing stock statuses, we employed those finer divisions.

More about the map legend Extinct - Were present in the specified watershed at one time but are no longer found.
At Risk - Having escapements less than 1,000. Levels of escapement declining or stable after a period of decline. If intensive analysis confirms identity as a "distinct population segment," have likely attained the threshold for listing as "endangered" or "threatened" under the Endangered Species Act. Includes populations categorized as "High Risk" or "Moderate Risk" by fisheries biologists.
Special Concern - Believed to be vulnerable to minor disturbances, especially if a specific threat is known. Available data suggests depletion but is insufficient to conclude a trend. Face a large possibility of interbreeding with non-native and/or hatchery fish. Require attention because of a unique stock character.
Low or No Risk - Have been identified as being present within the specified watershed and are at no apparent risk of decline or extinction.
Not Evaluated - Information is insufficient to determine status.

Often, several populations of salmon share each watershed. The Pacific North American range is home to five species of salmon (chinook, chum, coho, pink, and sockeye) and two species of sea-going trout (steelhead and cutthroat). The cutthroat trout does not undertake an extensive ocean migration and was not included in this research. Some species are further divided according to their season of spawning migration: fall-run chinook are distinct from the same river's spring run.

This project follows in the footsteps of regional reviews performed for the Pacific Northwest (Nehlsen et al 1991), British Columbia (Slaney et al. 1996), and Southeast Alaska (Baker et al. 1996), compiling their findings as well as that of more than fifteen other sources.

Our synthesis serves to highlight how much, in fact, remains unknown. Throughout the North American range, only 7,391 out of 19,172 documented stocks (39%) have been assessed. In Alaska, only 10%. This lack of data severely constrains efforts to manage these fish and the human activities that affect them.

Among the resulting products of our effort are the maps at right, first published in Salmon Nation. In these maps, stocks were rated according to a scale of health, from "low risk of extinction" through "at risk" to "extinct." This scale compiles and aligns the data-collection formats and nomenclatures used by the various sources.

The maps at right portray the sharp dichotomy in the status of Pacific salmon stocks. North of Vancouver Island, while many areas remain unassessed, the studies that have been performed describe a relatively healthier situation. In the Pacific Northwest, by contrast, the prevalence of red-colored watersheds, representing the extinction of hundreds of stocks, starkly depicts the dire state to which much of the region has fallen.

This dichotomy forms the basis of differing management strategies. Addressing first the southern half of the bioregion, Ecotrust has developed a systematic regional approach to the restoration of Pacific salmon stocks in the Pacific Northwest. This strategy identifies priority basins for restoration and emphasizes the establishment of anchor habitats, or refuges, for salmon.

More about the map legend.

The complete series of individual stock status maps is available in our Archive.