Bighorn River Montana Hatch Chart | The Fly Fishing Place

South-central Montana, below Yellowtail Dam near Fort Smith. The Bighorn is one of the premier tailwater fisheries in North America - a cold, clear, nutrient-rich river flowing through the high plains of the Crow Reservation before joining the Yellowstone near Bighorn City. Yellowtail Dam moderates temperatures and creates ideal conditions for year-round trout growth. The result is exceptional densities of wild brown and rainbow trout averaging 15-20 inches, with fish over 20 inches common throughout the system.

The Bighorn flows through the Crow Indian Reservation. A tribal recreation permit is required in addition to a Montana fishing license. Permits are available at Fort Smith and from outfitters in the area. Check current regulations for the Bighorn - the river has special regulations including catch-and-release sections and bait restrictions. Respect reservation boundaries and private land along the corridor.

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

The river

The Bighorn fishes best in its first 13 miles below Yellowtail Dam - from the dam to Bighorn Access. The upper section (miles 1-3, from the dam to Three Mile Access) is catch-and-release only and holds the highest density of large fish. The middle section (miles 3-13) allows harvest with restrictions. Below mile 13 the river warms and the fishery changes character. Most guided trips and visiting anglers focus on the upper 13 miles.

The river is wide, relatively shallow, and wade-fishable throughout much of its length - though a drift boat dramatically increases access to the best water. The bottom is slick and wading can be demanding. Felt-soled waders or studded boots are strongly recommended.

Scuds, sowbugs, and midges are the year-round foundation of the Bighorn food base - always have imitations available regardless of what else is hatching. The river's exceptional productivity stems from this constant invertebrate availability rather than reliance on any single hatch.

Year at a glance

Month	Primary hatches	Also carry	Typical sizes
Jan	Midges	Scuds, sowbugs	Midge 20-26, scud 14-18
Feb	Midges	Scuds, sowbugs	Midge 20-26, scud 14-18
Mar	Midges, BWO	Scuds, early caddis	Midge 20-24, BWO 18-20
Apr	BWO, midges, caddis	Scuds, PMD start late month	BWO 16-20, caddis 14-16
May	PMD, caddis, BWO	Scuds, midges	PMD 16-18, caddis 14-16
Jun	PMD, caddis, pale morning dun	Scuds, yellow sally	PMD 16-18, caddis 14-16
Jul	PMD, caddis, yellow sally	Hoppers start, scuds	PMD 16-18, hopper 8-12
Aug	Caddis, hoppers, PMD	Ants, beetles, scuds	Hopper 8-12, caddis 14-16
Sep	BWO, caddis, hoppers	Scuds, mahogany dun	BWO 16-20, hopper 8-12
Oct	BWO, midges	Scuds, October caddis	BWO 16-20, midge 20-24
Nov	Midges, BWO	Scuds, sowbugs	Midge 20-26, BWO 18-20
Dec	Midges	Scuds, sowbugs	Midge 20-26, scud 14-18

January

The Bighorn is one of the few rivers in the West that fishes well year-round, and January is no exception. Midges are the primary food source - the river's constant cold temperatures from the dam keep conditions stable and fish active even in the coldest months. Focus on slow to moderate-speed water 2-4 feet deep. Fish hold tight to the bottom and will move for a well-presented midge cluster or larva.

Midges - 20-26. Red zebra midge and small Euro nymphs subsurface. Midge cluster dry in size 18-20 when fish are dimpling.
Scuds - 14-18. Pink, orange, and olive scud patterns are year-round producers. Fish them on a long dropper below a midge.
Sowbugs - 14-16. Slow, dead-drifted in the weedy sections.

February

Same midge and scud program as January. February can produce exceptional midge dry-fly fishing on mild afternoons - look for dimpling fish in the flat tailouts and fish a small cluster or Griffith's Gnat above a midge larva dropper. The upper catch-and-release section holds the most fish and is worth the extra effort to reach in February.

Midges - 20-26. Red zebra midge and Euro nymphs. Griffith's Gnat 18-20 when fish are rising.
Scuds and sowbugs throughout.

March

March brings the first BWO activity on the Bighorn - gray overcast days trigger afternoon hatches that can produce excellent dry-fly fishing on the flatter sections. Midges continue throughout the day. Early caddis begin on the warmer spring afternoons by late month. Scuds and sowbugs remain the subsurface foundation.

BWO - 18-20 on overcast afternoons. Parachute BWO when fish are rising to the surface.
Midges - 20-24 throughout. Red zebra midge subsurface.
Scuds and sowbugs - year-round staples.

April

April is a transition month - BWO hatches strengthen and caddis begin in earnest by mid-month. PMDs can start on the Bighorn as early as late April in warm years, earlier than most Montana rivers due to the tailwater's stable temperatures. The dry-fly season is building and April can produce excellent mixed-hatch fishing with BWO in the morning and caddis in the afternoon and evening.

BWO - 16-20. Parachute BWO on overcast days.
Caddis - 14-16. Elk hair caddis afternoons and evenings.
Scuds and sowbugs subsurface throughout.
Late April: first PMD - 16-18. Pale Morning Dun.

May

The prime season opens in May. PMDs are the centerpiece - morning hatches that can last several hours with large fish rising across the flats. Caddis continue into the evening. The combination of PMDs, caddis, and BWO on overcast days makes May one of the best months on the Bighorn. Crowds begin building by late May - book guides and lodging well in advance.

PMD - 16-18. Pale Morning Dun mornings. Add a PMD nymph dropper on a two-fly rig.
Caddis - 14-16 afternoons and evenings. Elk hair.
BWO on overcast days. Parachute BWO.
Scuds and sowbugs as the subsurface baseline.

June

June is peak season on the Bighorn. PMDs continue strong through the month - the Bighorn's PMD hatch is one of the most reliable and dense in Montana. Caddis evenings are excellent. Yellow sallies begin in the riffles. The river sees heavy pressure in June - fish early and late, focus on the upper catch-and-release section for the best fish-to-angler ratios.

PMD - 16-18. Pale Morning Dun mornings. One of the best PMD rivers in the West.
Caddis - 14-16 evenings. Elk hair.
Yellow sally - 14-16 in the riffles on warm afternoons. See dry flies.
Scuds year-round subsurface.

July

PMDs continue into July - one of the longer PMD windows in Montana. Hoppers begin along the grassy banks and cottonwood-lined shores by mid-month. Caddis evenings remain strong. The Bighorn's wide, open character means hoppers can draw strikes from a long distance - fish them with confidence along the cut banks and weed edges. July is the busiest month on the river.

PMD - 16-18. Pale Morning Dun mornings.
Caddis - 14-16 evenings. Elk hair.
Yellow sally - 14-16 in the riffles.
Early hoppers along the banks - hoppers and terrestrials. Hopper-dropper with a scud or nymph dropper.

August

Hopper fishing is at its peak in August - the Bighorn is one of Montana's premier hopper rivers. Fish them tight to the cut banks and along weed lines. Caddis evenings continue. PMDs linger into early August on the upper section. Ants and beetles fill the midday window. Monitor water temperatures - the Bighorn can warm in August and fish may become sluggish midday. Fish early morning and evening for the best action.

Hoppers - 8-12. Hoppers and terrestrials along the banks. Hopper-dropper with a scud or small nymph.
Caddis - 14-16 evenings. Elk hair.
Ants and beetles midday from hoppers and terrestrials.
Scuds year-round subsurface.

September

September is arguably the best month on the Bighorn. Crowds thin after Labor Day, BWO return with the cooling temperatures, hoppers continue through mid-month, and the fish are in prime condition before winter. The fall BWO hatch on the Bighorn is outstanding - dense afternoon hatches on gray days over fish that are more willing than during the pressured summer months. Mahogany duns add variety on overcast afternoons.

Hoppers through mid-September. Hoppers and terrestrials.
BWO - 16-20. Parachute BWO and CDC Baetis emerger on overcast afternoons.
Mahogany dun - 14-16 on overcast afternoons.
Scuds and sowbugs subsurface throughout.

October

Fall BWO fishing continues and strengthens through October - the best dry-fly hatches of the fall season. Midges begin reasserting themselves as the primary food source as temperatures drop. October caddis add a large dry-fly option on warmer afternoons. Streamers produce well in October as brown trout begin pre-spawn aggression - big articulated patterns and sculpin imitations draw strikes from the largest fish of the year.

BWO - 16-20. The dominant dry-fly hatch. Parachute BWO.
Midges - 20-24 picking back up. Red zebra midge.
October caddis - 8-10 on warmer afternoons.
Streamers for pre-spawn browns - streamers. Articulated patterns and sculpin imitations in the deeper runs.

November

Midges and BWO dominate as the season winds down. November is underrated on the Bighorn - very few anglers, stable tailwater temperatures, and fish that are less pressured than any other time of year. The midge dry-fly fishing on mild afternoons can be outstanding. Scuds and sowbugs produce subsurface throughout the month.

Midges - 20-26. Red zebra midge and small nymphs. Midge cluster dry when fish are rising.
BWO - 18-20 on overcast afternoons. Parachute BWO.
Scuds and sowbugs - 14-18 subsurface.

December

Back to the winter midge and scud program. The Bighorn's tailwater character keeps the fishery productive year-round - December on the Bighorn is better than June on many other Montana rivers. Focus on the slower water adjacent to the main channel, present midges slowly and naturally, and expect fish from 15 inches to over 20 throughout the winter.

Midges - 20-26. Red zebra midge and Euro nymphs subsurface. Midge cluster or Griffith's Gnat dry when fish are dimpling.
Scuds - 14-18. Pink and olive. Year-round Bighorn staple.
Sowbugs - 14-16 in the weedy sections.

A western dry and nymph assortment covers the core season. Supplement with a dedicated midge selection for the winter months, scud and sowbug patterns year-round, and a hopper box for August and September. The Bighorn rewards the angler who knows the subsurface game - scuds and midges catch fish every day of the year, and the PMD and hopper windows are as good as anything in Montana.