Gallatin River Montana Hatch Chart

Southwest Montana and northwest Wyoming. The Gallatin River rises in Yellowstone National Park near the west edge of Yellowstone Lake, flows north through the park's broad meadow plateau, and then drops into a narrow granite canyon as it crosses into Montana near West Yellowstone. From there it runs 120 miles north through the Gallatin Canyon and the Gallatin Valley before joining the Missouri River at Three Forks.

The Gallatin holds wild rainbow and brown trout throughout, with cutthroat in the upper park water. The canyon section between Big Sky and Bozeman is the most accessible and most fished reach — a fast, technical freestone river with good hatches and fish that see significant pressure. The upper river in the park is slower, meadow-like, and holds mostly cutthroat. The lower valley below Bozeman is warmer and slower, with larger brown trout but less consistent surface fishing in summer.

Check current Montana FWP regulations before you go. The park section follows National Park Service rules — a park fishing permit is required and regulations differ from Montana state rules. The canyon below the park boundary is Montana water. Portions of the river can be subject to hoot owl restrictions during warm summer periods — check conditions before fishing in July and August.

Shop by type: dry flies, nymphs, Euro nymphs, hoppers and terrestrials, streamers.

The two sections

Park stretch (Wyoming) — Yellowstone National Park

Slow meadow water in the upper park, flowing through open flats near the Yellowstone Lake plateau before entering the canyon at the Montana border. Mostly Yellowstone cutthroat with some rainbow. Backcountry access; the upper reaches require significant hiking. Hatches run two to three weeks behind the canyon below. A Yellowstone National Park fishing permit is required — no Montana fishing license applies here.

Canyon and valley (Montana) — West Yellowstone to Bozeman

The primary fishery. Fast, rocky canyon water from the park boundary through Big Sky and down to Manhattan. Wild rainbows and brown trout, good road access along US-191, and one of the most productive freestone hatch calendars in Montana. The canyon narrows dramatically below Big Sky — steep walls, pocket water, and fast riffles. Below Bozeman the river slows and warms; best early season and fall.

Year at a glance

Month Primary hatches Also carry Typical sizes
Jan Midges BWO on mild days, stonefly nymphs 18-22
Feb Midges, BWO Small dark stonefly nymphs 16-22
Mar BWO, midges Skwala start on lower canyon 16-22, Skwala 8-12
Apr BWO, Skwala, March Brown Early caddis, streamers 12-18
May Caddis, BWO, stonefly nymphs Runoff builds mid-month Caddis 14-16, BWO 16-20
Jun Salmonfly, golden stone, caddis PMD late month Stones 4-10, caddis 14-16
Jul PMD, caddis, yellow sally Hoppers start, monitor temps 14-18
Aug Hoppers, caddis, ants Late PMD, beetles - monitor temps Hopper 8-12, ant 14-16
Sep Hoppers, BWO, mahogany dun Streamers for pre-spawn browns 10-18, BWO 18-20
Oct BWO, mahogany dun, October caddis Midges, streamers for browns BWO 18-22, caddis 8-12
Nov BWO, midges Streamers for post-spawn browns 18-22
Dec Midges Small nymphs, streamers 18-22

January

The canyon fishes year-round. January midge activity can be good on calm, mild afternoons in the lower canyon near Bozeman. The upper canyon near Big Sky is cold and often iced along the edges. Fish hold in slower inside bends and deep tailouts. The park stretch is closed to fishing in winter.

February

Same midge program with increasing BWO activity on overcast afternoons. The lower canyon and valley water near Bozeman can produce good midday fishing on milder days.

March

BWO pick up as days lengthen. Skwala stoneflies begin on the lower canyon when water temperatures climb out of the low 40s — the Gallatin is one of the better early Skwala rivers in Montana. Streamer fishing for pre-runoff browns picks up through the canyon in March.

April

Olives, March Browns, and Skwala provide dry-fly opportunities on gray days. Caddis begin late in the month. Runoff typically starts building toward the end of April — fish the first half of the month. The park section opens to fishing on the Saturday of Memorial Day weekend.

  • BWO and March Brown, 12-18, on cloudy afternoons.
  • Skwala on warm bank water in the lower canyon.
  • Early dark caddis at dusk.
  • Streamers in off-color water as flows begin to rise.

May

Caddis hatches can be excellent in early May before runoff peaks. The Gallatin canyon typically blows out mid-month with snowmelt from the Gallatin Range. The lower valley near Bozeman clears earlier than the canyon. The park stretch opens late May and is worth visiting for uncrowded cutthroat fishing once runoff settles.

June

The salmonfly hatch is the signature event on the Gallatin. As flows drop and clear — typically mid-to-late June — the hatch moves upstream through the canyon. The narrow canyon walls concentrate fish and anglers; the best dry-fly fishing often happens on the leading edge upstream of the main hatch. Golden stones follow and extend the big-bug window into early July. The park stretch sees PMDs and caddis but no salmonfly — the canyon is where you want to be in June.

  • Salmonfly - 4-8. A West Fork Salmonfly tight to the canyon walls and undercut banks. Fish the leading edge upstream of where adults are thickest.
  • Golden stone - 6-10. Overlaps and follows the salmonfly. Drop a stone nymph 18 inches below a dry.
  • Caddis - 14-16 evenings. Elk hair.
  • Late June: first PMD in riffles, 16-18. Pale Morning Dun.

July

Classic summer dry-fly fishing in the canyon. PMDs in the morning, caddis in the evening, hoppers beginning along the grass banks. The canyon sees heavy float and wade traffic in July — early morning is the best window for solitude and rising fish. The park stretch is at its best in July: uncrowded meadow water, willing cutthroat, and excellent caddis and PMD hatches. Monitor water temperatures in the lower canyon and valley in late July.

August

Hopper season in the canyon. The Gallatin's fast canyon water stays cooler than valley rivers, but temperatures in the lower canyon and valley can still reach stress levels in August during hot years. Check conditions before fishing midday on the lower river; the upper canyon and park stretch stay cooler longer. Fish early, release quickly.

  • Hoppers, ants, beetles - hoppers and terrestrials. A hopper-dropper with a small nymph underneath covers both feeding lanes along the canyon walls.
  • Evening caddis. Elk hair.
  • Late PMD on cool mornings in the upper canyon.

September

One of the best months on the Gallatin. Hoppers hold through mid-September. Mahogany duns and olives arrive as nights cool. Brown trout in the canyon begin staging ahead of the spawn — the largest fish of the year move into feeding lanes and respond to dries and streamers. The park stretch closes at the end of October. Crowds drop sharply after Labor Day.

  • Hoppers and ants through mid-September.
  • Mahogany dun - 14-16 on gray afternoons.
  • BWO - parachute BWO and Baetis emerger, 18-20.
  • Streamers at first and last light for staging browns.

October

Fall colors in the canyon and aggressive pre-spawn brown trout. October caddis and olives for willing fish. Streamer fishing through the deeper slots and undercut canyon walls can produce the largest fish of the year. The park stretch closes at the end of October — fish it early in the month while it's still open. Handle spawning fish carefully.

  • October caddis - 8-12, large orange dry.
  • Mahogany dun and BWO on overcast days.
  • Midges in slow tailouts and pools.
  • Streamers for brown trout through the canyon's deeper holding water.

November

Spawning winds down. Cold mornings, short days. BWO and midges in the warmest part of the afternoon. Post-spawn browns hold in the deeper canyon runs and respond to streamers swung slowly through slower water.

  • BWO and midges, 18-22.
  • Streamers in deeper, slower canyon runs.
  • Small nymphs through holding lies.

December

Midge and nymph program. The lower canyon near Bozeman is the most accessible option. Cold, clear water and fish that will eat a well-presented midge on a calm afternoon.

A western dry and nymph assortment covers the core season. Add a salmonfly pattern, hoppers, mahogany duns, and a streamer box for the complete Gallatin experience — and don't overlook the park stretch in July for uncrowded cutthroat on small dries.