I have yet to find a mountain lake that a woolly bugger is not the fly preferred by the fish (and me, because they are so effective), unless there is a hatch going on. I disagree with the general comment that these food sources are "low priority". Fish eat what they can in the short time they have available, and a woolly bugger, whatever it represents to a fish, is a LARGE meal. I also have seen leeches in many, many high lakes in both the cascades and rockies, as well as dragons and damsels, tadpoles, and other large and presumably tasty meals. The highest lakes, in granite basins, with the lowest productivity, may have limited food for trout, but buggers still produce fish in those conditions. In my experience, anyway.
And one easy way of catching fish in those lakes, especially with a short range system like Tenkara, is to walk the banks, watch for a cruising fish, and plop a bugger in front of it.