With spruce moths now over on the Gallatin River we are just waiting for fall Blue Winged Olives to come. The river is low and these fish always have a busy summer with all of the tourist anglers and rafters, so to catch fish on the Gallatin River right now, the best bet is going to be fishing small nymphs subsurface below an indicator or below an attractor dry fly or terrestrial. Leaders most likely will need to be long and if you are fishing subsurface opt for fluorocarbon. Flows are low, clear, and the algae isn't too bad so anglers looking for some local Bozeman or Big Sky fly fishing action should find some success on the Gallatin River. The nights are getting cool in Gallatin Canyon so there isn't a big rush to get on the water early.
Nymphing the deeper runs with a stonefly on top and a smaller mayfly nymph on point is also very effective. The Gallatin River should continue to provide great fishing for the next few weeks. The trout are still in the softer water along banks, rocks and it tailouts. Fishing is best in the later morning and mid afternoon when water temps are ideal and trigger hatches. Trout are eating both dries and nymphs. Attractor dry flies are just starting to produce and a dropper rig is a nice option. In the deeper runs try running a nymph rig with a stonefly trailed by a smaller bead head attractor nymph. Cover a lot of water but pay attention to where you are finding trout. They are often still giving preference to slower flows while the water temps are rising and are not all in the fast riffles yet. The wade fishing can still be challenging even with the lower flows.
The river in Gallatin Canyon near Big Sky and into Yellowstone National Park, this is one of the better options for DIY anglers right now for anyone wanting some good walk and wade fishing. The river is flowing around 600 CFS which is a great level for walk and wade fishing on the river in the Big Sky and Bozeman areas. The best fishing right now is up in the canyon. In the valley a very early start is advised due to high water temperatures. The Spruce moths are also on the water early in the morning in the canyon before the sun hits the water. Fishing slows down after lunch and then picks up again in the hour before dark.
Water temps are good all day in the canyon but in the valley they heat up fast so be careful of fishing later into the day if you are low down river. The morning fishing has been better than afternoon and spruce moths are on the water in the morning before the sun gets too strong. Nymphing smaller patterns on 5x flourcarbon can be effective when they aren't chasing spruce moths up high or hoppers down low.
Flies for the Gallatin River for the Next Few Weeks:
Perdigons #14-18
FKA Prince #12-16
Blowtorch #14-18
Flutter Bug #6-8
Chubby #8-16
Foam Run Caddis #14-16
Mini Dungeon #4-8
Sculpzilla #4-8
The Month Ahead:
The Gallatin River is going to start fishing better and better the more we get into September. It is low so best to use small flies--tandem nymph rigs are the best bets right now on long leaders and light tippets.
Long Term Fishing Forecast
The Gallatin River near Big Sky and Bozeman will be a good option all fall. By mid-September the valley fishing improves as temperature drops. Baetis hatches in late September and October can produce some dry fly action.