SNAKE RIVER SALMON AND THE ENDANGERED SPECIES ACT Snake River sockeye salmon were listed as an endangered species on November 20, 1991. Snake River spring/summer and fall chinook salmon were listed as threatened on April 22, 1992. However, due to record low returns in 1994, NMFS proposed to reclassify Snake River chinook salmon as endangered. Many factors played a part in reducing these salmon populations to the point of listing under the ESA. Creation of dams and reservoirs in their migration corridors and the loss and deterioration of their spawning and nursery habitats are the primary factors while disease, predation, excessive harvest, water being withdrawn from streams for other uses, and impacts from hatchery fish, are among the other causes. Impacts of climate change are also considered a significant factor for decline (i.e., El Nino and prolonged drought conditions). Snake River sockeye salmon have declined in abundance more than the other Northwest salmon. During the 1950s and 1960s, as many as 4,300 adult sockeye returned from the ocean to Redfish Lake, Idaho, to spawn. In 1992, one adult sockeye returned to Redfish Lake, in 1993, eight returned, and in 1994, only one sockeye returned. Naturally produced Snake River fall chinook salmon have also declined to small numbers. At the uppermost Snake River dam with fish passage, an average of 12,700 salmon passed the dam from 1964 through 1968. Fish passing the dam fell to a low of 78 in 1990, and then increased to 318 in 1991, 533 in 1992, 742 in 1993, and 404 in 1994. Exact numbers of naturally produced Snake River spring/summer chinook salmon are harder to obtain because many hatchery spring/summer chinook salmon have been released in the system. However, from 1950 through 1960, approximately 125,000 naturally produced adult spring/summer chinook annually returned to the system. Estimated returns of natural spring/summer chinook averaged 9,600 from 1980 through 1990. In 1991 and 1992, 3,400 spring/summer chinook returned to the Snake River Basin, in 1993, 7,900 returned, and in 1994, 1,800 returned to spawn.

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