The only places in Yellowstone that are crowded are the famous rivers, and even those are uncrowded if you fish in the right spots and at the right time of day. We have a spot on Slough Creek where we take clients on day trips where we usually don't see anybody and catch fish to 22 inches, for example.

Even without a guide, the small streams are virtually always empty once you get 100 yards off the road or away from the campground. If you are in good enough shape to walk/scrample, you can catch all the 6-12 inch fish you want without having to detour around anybody else.

www.parksflyshop.com/planner.htm for more info.