ABSTRACT
In response to petitions to list coho salmon Oncorhynchus kisutch under the U.S. Endangered Species Act (ESA), the National Marine Fisheries Service (NMFS) initiated a status review of coho salmon in the Pacific Northwest and formed a Biological Review Team (BRT) to conduct the review. The BRT identified six evolutionarily significant units (ESUs), or “species” under the ESA, for coho salmon and evaluated the risk of extinction for these ESUs. Identification of these ESUs was based on genetic, life history, biogeographic, geologic, and environmental information. The six ESUs encompass coho salmon habitats from the southern limit of their range in Monterey Bay to tributaries flowing into the north end of the Strait of Georgia. Both qualitative and quantitative information were used to assess extinction risks faced by these ESUs. This information indicated a latitudinal trend in stock health, with coho salmon in the southernmost ESUs facing the greatest risks and those in the northern ESUs facing fewer risks. Based on this latitudinal trend in stock health, and on present conservation efforts, NMFS proposed listing three coho salmon ESUs south of the Columbia River as threatened under the ESA. Of the three remaining ESUs, only one was not proposed for listing. The other two were identified as “candidate” species, for which listing may be warranted in the future. Since the NMFS proposed listings, the three southernmost ESUs have been listed as “threatened” under the ESA and the fate of the remaining candidate ESUs are being determined as of this printing.
