Bighorn River, MT

About Bighorn River

The Bighorn River in south-central Montana is one of the most celebrated tailwater trout fisheries in the United States. The reach that anglers come for begins below Yellowtail Dam near Fort Smith, where the river emerges from the bottom of Bighorn Lake as cold, clear, nutrient-rich water flowing across the Crow Reservation. This stable, year-round cold-water release transformed the lower Bighorn into a trout factory, supporting extraordinary numbers of wild trout per mile and drawing fly anglers from around the world.

What the Bighorn is best known for is its combination of density and size: thousands of wild trout in the upper few miles below the dam, fish that are well-fed on prolific insect hatches, and a tailwater that fishes well in nearly every month of the year. The classic float is the upper stretch from the dam down through a series of long riffles, deep runs, and gravel flats, and the river's reputation for technical, rewarding dry-fly and nymph fishing has made it a bucket-list destination for trout anglers.

Fish Species

The Bighorn below Yellowtail Dam is fundamentally a trout fishery, and that is what virtually everyone targets:

• Brown trout — the backbone of the river and the species the Bighorn is most famous for. Wild, healthy, and present in remarkable numbers, with plenty of solid fish and a real shot at a true trophy.
• Rainbow trout — abundant, strong-fighting, and often willing players on both nymphs and dries; they make up a large share of the catch alongside the browns.

Other species occur in the system, particularly as you move farther downstream and water warms, where you may encounter mountain whitefish and various warm-water and rough fish. But the headline fishery, and the reason the Bighorn has its reputation, is the wild brown and rainbow trout in the cold tailwater reach.

Best Seasons & Times

One of the Bighorn's greatest strengths is that it is a true year-round fishery thanks to the steady cold flows from the dam.

• Spring: Excellent fishing as the river warms. Look for strong baetis (blue-winged olive) hatches on overcast days, along with steady midge activity. Pre-runoff conditions are usually clear and productive, and spawning browns and rainbows are active around the edges of the season.
• Summer: Prime time for hatches. Pale morning duns (PMDs) and caddis bring fish to the surface, and there can be tremendous dry-fly and emerger fishing. Mornings and evenings are best when daytime sun and crowds push fish down; terrestrials like hoppers, ants, and beetles produce along the banks later in summer.
• Fall: A favorite for many regulars. Cooling water, fewer crowds, and aggressive pre-spawn brown trout, plus a return of blue-winged olive hatches on gray days.
• Winter: The tailwater stays open and fishable. Midges dominate, fishing is slower and more technical, but solo days on a famously busy river are the reward. Midday during the warmest part of the day is most productive.

Across the seasons, overcast, drizzly days often produce the best mayfly hatches and surface action, while bright bluebird days push fish to subsurface tactics.

Techniques & Baits

The Bighorn is primarily a fly-fishing river, and most anglers fish it from a drift boat or by wading the gravel bars and riffles. Both nymphing and dry-fly fishing are highly productive depending on conditions.

• Nymphing: The day-in, day-out workhorse. Fish small midge larvae and pupa patterns, baetis and PMD nymphs, sowbug and scud imitations, and small attractor nymphs under an indicator through deeper runs and riffle seams. The Bighorn's trout are well-conditioned to size #16–#22 patterns and light tippet.
• Dry-fly fishing: When mayflies and caddis are coming off, target rising fish in soft seams and along banks with BWO, PMD, and caddis imitations, plus midge cluster patterns. Accurate drag-free drifts matter on this clear, pressured water.
• Streamers: A go-to for hunting larger brown trout, especially in spring and fall and on higher or off-color flows. Strip and swing streamers tight to banks, drop-offs, and structure.
• Terrestrials: In late summer, hoppers, ants, and beetles along grassy banks can draw explosive eats, and a hopper-dropper rig covers both the surface and subsurface zones.

Light tippets, small flies, and clean drifts are the recurring theme. Because the river is technical and crowded in peak season, a guided float is a common and effective way for first-timers to learn the water and the hatches.

Access & Launches

The most popular and productive water is the tailwater reach below Yellowtail Dam near Fort Smith, Montana, on the Crow Reservation. Anglers commonly access the river through established public access points and developed boat launches along the upper stretch, and the classic experience is a drift-boat float between launch and takeout sites, with wade fishing on gravel bars and side channels along the way.

Fort Smith is the hub for the fishery, with lodges, fly shops, and guide operations that provide boats, shuttles, and local knowledge. Because much of the surrounding land is the Crow Reservation and private property, be mindful of land ownership and access rules when leaving the river corridor. If you are not floating with a guide, plan your put-in and take-out in advance, and consider hiring a local shuttle service. Always confirm current access conditions, ramp availability, and any tribal or local permit requirements before your trip.

Regulations & Licenses

A valid Montana fishing license is required to fish the Bighorn River, and anglers should review current Montana Fish, Wildlife & Parks regulations before heading out. Because portions of the river flow through the Crow Reservation, there may be additional tribal access or permit considerations depending on where and how you fish, so check current requirements in advance.

Trout regulations on the Bighorn may include specific size, slot, and bag limits, as well as gear or seasonal restrictions, and these can change from year to year. Many anglers practice catch-and-release to protect this wild trout fishery. Always confirm the current rules with the state wildlife agency (and any applicable tribal authority) before fishing, and follow all posted regulations.

Frequently Asked Questions

What kind of fish is the Bighorn River known for?
The Bighorn below Yellowtail Dam is a world-class tailwater trout fishery, famous for high numbers of wild brown trout and rainbow trout. Browns are the marquee species, but rainbows are equally abundant and provide much of the action. It is not a warm-water or bass destination — it is all about trout.

When is the best time to fish the Bighorn River?
The Bighorn fishes year-round thanks to cold, stable flows from the dam. Spring and fall offer excellent baetis (blue-winged olive) hatches and active fish with fewer crowds, while summer brings prime PMD and caddis dry-fly fishing. Winter is slower and midge-driven but offers solitude. Overcast days and the morning and evening windows are typically most productive.

Do I need a guide or boat to fish the Bighorn?
You don't strictly need one, but a guided drift-boat float is the most common and effective way to experience the river, especially for first-timers. The fish are technical and the water is heavily pressured in peak season. Wade fishing the gravel bars and riffles is very productive too, but you'll want a shuttle plan and good knowledge of the hatches and access points.

What flies work best on the Bighorn River?
Small subsurface patterns dominate: midge larvae and pupa, sowbugs and scuds, and baetis and PMD nymphs in roughly size 16 to 22 under an indicator. When mayflies and caddis hatch, switch to matching dry flies and emergers. Streamers are the play for big browns, especially in spring and fall, and hoppers and other terrestrials produce along the banks in late summer. Light tippet and clean, drag-free drifts are key.