As the end of July draws near, all of us at BSA hope you have been able to find some exciting fishing in Yellowstone thus far. With warmer August days on the horizon, we begin to dust off those terrestrial boxes and look forward to throwing hoppers, beetles, and ants.
The Northeast corner of the park continues to be a shining example of prime dry-fly water. Getting into the West entrance before 7am is ideal when making the drive out there. The Lamar, Soda Butte, and Slough Creek will all present unique opportunities within a full days venture. Have a variety of cream/rusty duns and spinners along with your terrestrials if you plan on hiking up Slough. Bring bear spray and make noise while hiking. Make sure to stop and enjoy all the wildflowers! If you've never spent time in this area of the park, now is an excellent time to make the voyage.
Always pay attention to bugs in the air, water, and grass to clue in your fly selection. Water conditions are usually low and clear at this point in the season, so slowing down your approach and spending extra time observing fishy looking areas is helpful. Remember, big trout don't like undercut banks, so it's best not to waste time fishing a size 14 Jake's Gulp Beetle under overhanging, shady banks.
The Upper Yellowstone is still fishing well, although those big cutties have seen a fly or two by now. Focus on getting into a good angle and then making a clean, drag-free first presentation. Stalk more, cast less. As for the lower river, caddis and dry dropper rigs topped with chubbies, water walkers, hoppers, etc. have still been producing. Besides those soulless perdigons, try hanging a PT frenchie, tungsten red neck, or a rainbow warrior for a dropper(sz 14-16).
Spending an hour or two stripping Bouface leeches/buggers on Yellowstone Lake in the mornings/evenings can be tricky but rewarding. Look out for cruising fish eating callibaetis or flying ants as well. Many park stillwaters are in their prime during this time.
The Gallatin has seen decent fishing with PMDs and caddis close to the bank. The terrestrial fishing should turn things up a notch in the coming weeks. The southwest corner of the park can provide the intrepid and well-informed angler with large trout through the next month onwards. We're still largely leaving the fish in the Firehole and Madison alone for the time being. Good luck out there!