Bighorn River, Montana Fishing Guide

The Bighorn below Yellowtail Dam is a tailwater trout river with steady flows and very high numbers of brown and rainbow trout. Most anglers drift from the Afterbay to 3 Mile or 13 Mile and stop to wade, fishing nymphs, midges and dry flies. Access is limited by Crow tribal and private land, so stay in the river below the high-water mark.

📍 South-central Montana at Fort Smith, below Yellowtail Dam and the Afterbay Dam in Bighorn Canyon National Recreation Area. The upper river runs through the Crow Reservation. Public access on the upper 13 miles is at the Afterbay (River Launch), 3 Mile (Lind Ranch) and 13 Mile (Bighorn Fishing Access Site).

Map: spots, ramps and marinas

★ Fishing hot spot · ● Boat ramp · ● Marina · ▭ Protected area (solid red = no fishing, dashed = fishing with rules)

Open the full Rocky Mountain Trout Rivers map →

Quick facts

Yellowtail Dam stands 525 feet high; it was completed in 1967 and dedicated on October 31, 1968.
The dam made the Bighorn a cold, clear tailwater that stays ice-free in winter; the river has been open to the public since 1981.
FWP's 2025 surveys estimated 2,446 trout per mile (over 7 inches) in the upper section, about half rainbows and half browns, and 2,187 per mile in the lower survey section.
There are only three public access points on the upper 13 miles; land above the high-water mark is almost all Crow tribal or private land.
A Montana fishing license is required on the Bighorn inside the Crow Reservation; a tribal permit is not required.

What you can catch

Brown trout
One of the two main trout; FWP counted 531 browns per mile in the lower 2025 survey section.
Rainbow trout
Rainbow numbers more than doubled in FWP's 2025 survey compared with 2024.
Afterbay trout
Rainbow trout are the main fish in the Afterbay Reservoir just below Yellowtail Dam.
Common carp
Present in the river; not often targeted.
Shad
The Park Service says shad spawn in the river in fall.
Other fish
The Park Service says 38 species of fish have been caught in Bighorn Canyon waters.

Month by month

January	Open all year; the tailwater stays ice-free. Midges, scuds and sowbugs below the surface.
February	Midges; fish the warmest part of the day.
March	Montana license year starts Mar 1. Blue-winged olives start in early March.
April	Blue-winged olives, best on overcast days; midges continue.
May	Blue-winged olives through May. Crowds start to build late in the month.
June	Flows often peak in June (often above 7,000 cfs). PMDs start mid-June.
July	PMDs and strong tan and black caddis; tricos start mid to late July; terrestrials by late July.
August	Flows usually around 2,500 cfs. Tricos at sunrise, hoppers midday, black caddis at dusk. Hoot-owl limits may apply if water warms.
September	Fall blue-winged olives from mid-September; crowds thin after Labor Day. October caddis start late in the month.
October	Blue-winged olives; October caddis peak in mid-October. Streamers for pre-spawn browns.
November	Midges and late blue-winged olives; fewer anglers.
December	Midges and small nymphs; scuds and sowbugs year-round.

Tips

Buy a Montana Conservation License, AIS Prevention Pass (16+) and Fishing License; you do not need a Crow tribal permit.
Stay below the high-water mark (where land plants start). Trespassing on Crow tribal or private land can mean a citation and fines.
From the cable 600 feet below the Afterbay Dam down to the Bighorn FAS, use artificial lures only.
Give other anglers room: the Park Service asks drifters to stay about 40 yards from waders and to pass slower boats well downstream.
Do not walk on spawning gravel during or just after spawning.

Rules and license

Montana Fish, Wildlife & Parks (Central Fishing District); National Park Service, Bighorn Canyon NRA (access sites) · Official rules page ↗

Montana license required: Conservation License + AIS Prevention Pass (16+) + Fishing License; also required inside the Crow Reservation, no tribal permit needed.
Cable 600 feet below Afterbay Dam to Bighorn FAS: artificial lures only.
Live nongame bait fish allowed only from Afterbay Dam to the cable 600 feet downstream, and below the Bighorn FAS.
Central District standard limit applies where no exception is listed: 3 trout daily, only 1 over 18 inches.
Central District rivers are open all year (2026 rules).
Motorized boats are restricted from Afterbay Dam to the Bighorn FAS (FWP boating rules; the Park Service says motors are prohibited on the upper 13 miles).
All boats must pass an aquatic invasive species check before launching.
Hoot-owl (2 p.m.-midnight) restrictions may apply when water stays warm; check fwp.mt.gov/news/current-closures-restrictions.

Rules change. Always check the official page before you fish.

Boat ramps and marinas

The map above shows 5 boat ramps and 0 marinas from OpenStreetMap. Tap any dot for directions.

Sources

Checked October 2026. BigJoe does not invent facts: every number on this page comes from the sources listed above.