Don,
Your statement that only "4 of 13" ESA stocks in the Columbia River are located in the Snake River Basin ignores a very important point: the Snake River drainage is massive. This is the largest area of spawning habitat for salmon and steelhead on the Columbia River and also historically produced more biomass than any of the other Columbia River tributaries.  There is a huge amount of viable habitat in the Snake River drainage that isn't being fully utilized.  Furthermore, other ESA listed salmon and steelhead in the Columbia system utilize the Snake before backtracking and moving into their drainages.  Most of the "record returns" of salmon are hatchery produced fish and not wild fish that spawned in their native rivers; the increased rate of return is largely attributed to better ocean conditions and less with the dam operations.  We've reached a point of diminishing returns on dam operations...each improvement will be more costly with less benefit.