In exchange for four Native tribes dropping lawsuits, the Bush administration will spend $900 million over the next decade to help out Northwest salmon. The settlement reached Monday ends, for the time being, a decades-long legal battle over the best balance of tribal and commercial fishing rights, protection for salmon, and regional power demands in the Columbia River basin. The new plan does not affect four hydroelectric dams on the basin’s Snake River, which environmentalists have long insisted must be torn down if salmon are going to see any benefit. The dam question will likely crop up again in early May, when the Bush administration brings a third try at a salmon-protecting plan to a district judge who has rejected two previous offerings as not protective enough.