In the mountain streams of the American West, the trout rules. People don't just catch this fish; they honor it. And spend lots of money pursuing it.
But some western trout may be in trouble. Rivers and streams are getting warmer and there's often less water in them. Scientists suspect a changing climate is threatening this iconic fish.
I joined two such scientists from the U.S. Geological Survey as they drove up a mountain road in Montana, in the northern Rockies, a place dense with stands of Douglas fir and aspen trees and braided with mountain streams.