Oncorhynchus kisutch

Apparently does not comprise genetically distinct, temporally segregated runs within a single river drainage, such as those that characterize the chinook salmon and steelhead trout; however, each coastal stream probably has a distinctive strain adapted to local conditions (Moyle et al. 1989). NMFS (1995) determined that there are six major stock groupings in the region extending from southern British Columbia to southern California.

Moyle et al. (1989) divided coho populations in California into two groups: "big river coho salmon" and "short-run coho salmon".

Still widespread around the margins of the North Pacific Ocean, and abundant in some areas, but logging and poor watershed management have caused many local extirpations and numerous declines; many runs are reported as now being of less than 25-50 individuals each.

Native range includes the Pacific Ocean and tributary drainages, in eastern Asia from the Anadyr River south to northern Japan and in North America from Point Hope, Alaska, south to central California and infrequently at sea as far south as Baja California. The species is most abundant between Oregon and southeastern Alaska, rare south of central California. It has been widely stocked in lakes and reservoirs throughout North America and elsewhere.

See Frissell (1993) for a map indicating present and former distribution in the Pacific Northwest and California. See Moyle et al. (1989) for further information on distribution in California.

In a survey of populations in the contiguous U.S., Huntington et al. (1996) identified only three healthy native stocks, all in Washington.

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.