Pacific salmon (see Table 10–1 for more information about terms in bold) enjoy iconic status in northwestern North America. As key components of both freshwater (Schindler et al. 2003) and marine (Beamish 2005) ecosystems, salmon play an important biological role in community structure and function. But salmon are no less crucial to the fabric of human societies. They have provided important food resources to Native Americans for at least 10,000 years (Butler & O'Connor 2004) and figure prominently in cultural, social, and economic traditions. Over the last ~200 years following European settlement, Pacific salmon have supported substantial commercial and sport fisheries, as well as continuing tribal harvest. Renowned for their long migrations and strong homing instinct, salmon have long been symbolic of Northwestern beauty and culture for human inhabitants of the region.

However, Pacific salmon also face a wide range of challenges to their persistence, due largely to major anthropogenic changes to their ecosystems (National Research Council 1996; Lackey et al. 2006). Urbanization, dams, road construction, harvesting, logging, mining, ranching, hatcheries, agriculture, invasive species, and other forms of habitat modification have all taken their toll on salmon populations. As a consequence, approximately 30% of historic salmon populations in the contiguous United States have been extirpated (Gustafson et al. 2007), and half of those that remain are formally protected under the U.S. Endangered Species Act (ESA) (Table 10–2).