Current Conditions:
The Gallatin River near Big Sky and Bozeman came up a good bit for this time of year but it has dropped and will most likely clear. Fishing prerunoff on the Gallatin River is ideal right now for wading anglers wanting a little DIY action. Hatches could be thick for Blue Winged Olives but caddis are a ways out. Midges will come off but if Blue Winged Olives pop trout will be keying on the larger mayflies compared to the tiny midges. For flies go with our list of Montana Angler fly shop staff picks. A tiny secret on the Gallatin River right now is how good the micro trout spey fishing can be. Pick a run, try out your cast, and see if you can swing up some fish.
It is unlikely it will get dirty in the next week or so, but trout in the Gallatin River still feed in dirty water, just be sure it still has some green or olive color to it. If it gets brown then perhaps consider the Lower Madison, but unless runoff begins in earnest--which is still unlikely because the night time temps are still cold--the Gallatin's trout will still feed in rising and dirty water. The warmer weather will melt some low elevation snow but anglers should still have plenty of legit weeks for this freestone.
Trout are still going to be in slower, deeper runs but will also be holding closer to current seams and feeding lanes as water temps rise and feeding activity increases. On rainy and snowy overcast days hatches of Blue Winged Olives (BWO) can be strong, midges can hatch un abundance as well, but the subsurface nymph game is where it is at on the Gallatin River right now. For anglers willing to kick over some stones and actively seek them out, a few skwala stoneflies can be found.
For nymphs a standard Gallatin River rig is a stonefly pattern in size 10 or 12--Pat's Rubber Legs is a top choice of local anglers. Follow the stonefly nymph with smaller beadhead mayfly or midge nymph. If Blue Winged Olives hatch look for fish to rise in a slow pool or slower current next to faster water.
An important component of fishing the Gallatin River right now is timing your day. Things start later on the Gallatin--give time for the water to warm up. If a BWO hatch occurs, bugs likely won't pop until between Noon and 2 PM. Midges can hatch earlier, but there is no need to be on the water any earlier than 10 or 11 am.
Our Fly Staff Picks for the Weekend:
Pat's Rubberlegs in brown/black in size 10 or 12
Beadhead FKA Prince in size 10
Hares Ear in size 14---if water isn't too dirty
Olive McCune's Scuplin size 8
Little Green Machine in pheasant tail in size 12---if not too dirty
Black Blowtorch in pheasant tail in size 12-16
Sparkle Dun in size 14 or 16
Sculpzilla in black in size 4 or 6
The Month Ahead:
The Gallatin River should remain a very legit option for fishing near Bozeman and Big Sky. Even as daytime high temperatures climb, the majority of the mountain snowpack that can cause the Gallatin River to start runoff is in elevations high enough to stay frozen. Hatches of BWOs and midges will dominate a trout's diet and the dry fly fishing and nymph fishing action should increase in duration throughout the angling day. A special thing to consider on the Gallatin is water color and clarity. Trout on the Gallatin River will feed in water that contains more color/sediment than many other rivers.