As of April 21st, Fins and Feathers, out of Bozeman, gave the Yellowstone River a 2/5 for fishing. Here is their report:
The Yellowstone River has about 2 feet of visibility and has some green color to it. Nymphing a Rubberlegs and a Baetis will be the best method to catch fish. Lightning Bugs, Prince Nymphs, Copper Johns and Perdigons have been finding a bunch of success as well. If that doesn’t work, the trusty worm will. Slow stripping or dragging small, dark streamers close to the bottom will give you a better shot at large trout but this method was very slow yesterday. Don’t be afraid to jig those streamers this time of year. Keep an eye out for rising fish. BWO’s and skwalas have been out a bit. A small olive body parachute pattern has worked well.