It is not just dams that cause salmon to be cut off from salmon habitat. Salmon fishing on the South Fork of the Salmon River ended in 1965 after extensive landslides, caused by logging and poorly constructed roads, smothered miles of spawning grounds with mud.31 Countless other such incidents have, tributary by tributary, reduced available habitat for salmon. Many comprehensive surveys are available showing, on a tributary by tributary basis, how particular examples of human development destroyed salmon habitat. If success in salmon recovery is defined to require naturally-spawning populations, salmon recovery may be a hundred-year war of trying to undo these developments piece by piece.
Rather than try to assess what the piece-by-piece habitat losses mean for attempts to recover salmon runs, fishery agencies tend to blame the dams for the effect of habitat loss. In 1973, the Fish Commission of Oregon reported that the number of redds per “standard spawning ground survey unit” in Idaho per 100 fish counted at the uppermost dam had dropped precipitously from the early 1960s to the early 1970s.32 The sharpest drop was from 1965 to 1966, which correlated with the mudslides in the Salmon River, not with anything relating to dams.
Yet the Fish Commission blamed the declines on delayed mortality, which they speculated was caused by dams. They did not explain how the effects only appeared after fish had passed all the dams. This was a precursor to the same "delayed mortality" claims fishery managers are now making about smolt transportation (see Chapter 5).
31 R. Barker, “Will anglers have a shot at South Fork’s salmon?”, The Idaho Statesman, Jan. 15, 1997.
32 Appendix to Special Report on the Lower Snake River Dams”, at 12 (Fish Comm’n of Oregon March 1973).
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