has been opened to additional anadromous frsh species (fall Chinook, summer steelhead) 

 due to the construction of the fishway at Willamette Falls. Throughout the Columbia River 

 system below Bonneville Dam. salmon and steelhead habitat has decreased from about 

 2.925 miles Of stream to about 2.491 miles of stream, about a 15 percent loss. 



Additional salmon and steelhead habitat throughout the Columbia Basin has been 

 degraded by forest and farming practices, waste disposal and other factors. In some areas 

 such habitat degradation has been extensive: these effects are. in principle, reversible. 

 Some rehabilitation has been carried out and more is anticipated as a result of a variety of 

 federal, state, local and private efforts. 



(d) Losses of Upriver Fish Runs and Habitat 



The greatest losses of fish runs and habitat have occurred in the upper Columbia and 

 upper Snake areas. These losses are largely unmitigated. Three general factors are 

 responsible for losses of upriver fish runs: a) Loss of habitat . As described in subsection 

 (c) above, habitat losses have been extensive, b) Mainstem passage mortality . Passage 

 mortality occurs at the mainstem dams and in the reservoirs formed by these dams. 

 Passage mortality currently is estimated to average about 15 to 30 percent per dam for 

 downstream migrants and 5 to 10 percent for upstream migrants. This has enormous 

 effects on upriver runs. As an example, cumulative juvenile passage mortality for fish 

 migrating downstream past nme dams can be estimated to be 77 to 96 percent, depending 

 on the volume and timing of runoff. Cumulative adult passage mortality for fish passing 

 nine dams upstream to spawning areas can be estimated to be 37 to 51 percent. These 



