Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: Many populations have been negatively impacted by logging, agricultural activities, overgrazing, urbanization, stream channelization, wetland loss, and poor watershed management practices that increase stream temperatures, cause siltation, or otherwise destroy or degrade habitat; road construction also has negatively altered many smaller coastal streams; dams, water withdrawals, and unscreened diversions for irrigation also have contributed to the decline. Poor ocean conditions (e.g., El Nino conditions) are believed to have played a prominent role in the decline of populations in Washington, Oregon, and California (NMFS 1995). The effects of extended drought on water supplies and water temperatures are a major concern for California populations of coho salmon. Native populations are most at risk in the southern and eastern parts of the range, largely as a result of the effects of successful hatchery programs (Nehlsen et al. 1991). Potential problems associated with hatchery programs include genetic impacts on indigenous, naturally reproducing populations, disease transmission, predation on wild fishes, difficulty in determination of wild run status due to incomplete marking of hatchery releases, and replacement (rather than supplementation) of wild stocks through competition and continued annual introductions of hatchery fishes (NMFS 1995). It is difficult to assess the degree to which recreational and commercial harvest have contributed to the decline. Spawning fish can withstand moderate disturbance. See NMFS (Federal Register, 6 May 1997) for further information on threats.
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