Fishing the Bighorn River: the trout, the hatches, and the plan to catch them

What and where it is

The Bighorn is the river below Yellowtail Dam in south-central Montana, near Fort Smith on the Crow Reservation. The dam releases cold, clear, steady water from the bottom of Bighorn Lake, which feeds dense insect life and a very high trout density. The classic stretch runs about 13 miles (21 km) from the Afterbay down to the Bighorn Access.

A tailwater is a river fed from the base of a dam, and that is the whole reason the Bighorn fishes the way it does. The water leaving Yellowtail Dam comes off the bottom of the reservoir, so it is cold and clear and its flow is regulated rather than at the mercy of summer drought or a spring freshet. Steady cold water grows huge numbers of scuds, sowbugs and midges, and the trout grow fat on them. The result is a river often quoted at thousands of catchable wild trout per mile (Montana FWP fisheries surveys and the Bighorn fly shops, as of 5 June 2026).

The top of the fishery is the Afterbay, a small regulating reservoir just below the main Yellowtail Dam, at the village of Fort Smith. From there the river runs roughly north, braiding through riffles, long runs and side channels, with the famous first three miles below the Afterbay holding the densest fish. The classic float is the 13 miles (21 km) from the Afterbay down to the Bighorn Fishing Access Site (Montana FWP / NPS Bighorn Canyon).

Two things shape any trip here. First, flow: the dam release sets the level, and a higher release pushes fish to the banks and slows the wading, while a low, clear release concentrates them in the channels. Check the current flow before you go (the fly shops post it daily). Second, access: much of the land along the river is Crow Tribal and private, so you fish from the boat or from the public access sites, not by wandering the bank wherever you like (see where to fish).

The trout, and where, when and how to catch each

Two trout carry this river: wild brown trout and wild rainbow trout, in big numbers and well fed. Whitefish are also present. You catch them on the fly: a nymph rig under an indicator for most of the year, a dry fly when the hatch is on, and a streamer for the bigger browns. The cards below give you where, when and how for each.

Whitefish, for context. The river also holds mountain whitefish, a native game fish that takes the same small nymphs and is no insult to catch on a slow day, plus a few warmwater species (sauger, ling) in the lower reaches that are a different fishery. Most visiting anglers come for the two trout, so the two cards above are the trip.

This is a two-species river, so I have set it out as two trout cards plus a note on whitefish. Read the card for the fish you want, check the seasonal section for what is hatching on your dates, then follow the rig link to build the method.

How the fishing changes through the year

The Bighorn fishes year-round because the tailwater stays cool and ice-free. Winter is midges. Spring (April to May) brings the baetis and strong nymphing. Mid-June to early September is the peak, with PMDs, tricos, caddis and the best dry-fly fishing. Autumn adds baetis again and the best streamer fishing for big browns.

Here is the year in plain terms, tied to the hatches the river is known for (Bighorn hatch charts and the Fort Smith fly shops, as of 5 June 2026).

• Winter (December to March). The river stays open and fishable. Midges are out every day of the year, so this is small-fly nymphing under an indicator, with a chance of risers to a midge dry on a still, mild afternoon. Quiet, cold, and you often have water to yourself. Sowbug and scud nymphs catch all winter.
• Spring (April to May). The baetis (blue-winged olive) hatch comes on, sizes 16 to 20, and the nymphing is strong with scuds, sowbugs and baetis nymphs. Cloudy, drizzly days bring the best baetis dry-fly fishing. A good, less crowded window.
• Early summer (June). Things ramp up. The PMD (pale morning dun) hatch starts around mid-June, sizes 16 to 18, and the dry-fly and emerger fishing gets going. This is the start of the peak.
• High summer (July to August). The peak. PMDs continue, the trico hatch begins in mid-July (tiny, sizes 18 to 20, with the spinner fall most mornings between about 9 and 11), and caddis fish in the evenings. Dawn and dusk beat the bright middle of the day. This is the busy season; book guides and lodging well ahead.
• Autumn (September to October). The baetis return on the cool, grey days, the crowds thin, and the streamer fishing for big browns comes into its own as they turn aggressive around the autumn spawn. Many regulars call this the best all-round window.

Can you eat what you catch

Legally you may keep a small number within the Montana limit, but in practice the Bighorn is fished almost entirely catch and release. The trout are wild and the fishery depends on returning them, so the culture and the fly shops are release-only. There is no consumption ban as such; this is a release fishery by choice, not a kitchen.

Be clear on the two separate things here. The law sets a limit (see the next section): on the river this is the standard Montana river trout limit, with most fish to be returned. The norm is that almost nobody keeps a Bighorn trout. The whole value of the river is the density of big wild trout, and that is sustained by releasing them, so the guides, the shops and the regulars treat it as catch and release whatever the bag limit technically allows.

If you do fish it as catch and release, which is the right call here, fish it well: pinch your barbs down so the fish come off cleanly, use a rubber-mesh net, keep the fish in the water, wet your hands before you touch it, and let it recover facing the current before you let go. Clean and dry your boots, waders and net between waters so you do not carry whirling disease, aquatic invasive species or anything else from one river to the next. Montana takes its aquatic-invasive rules seriously, which is why the AIS prevention pass is part of every licence.

Licence and rules

Yes, you need a Montana fishing licence from Montana Fish, Wildlife & Parks, and a state licence is required for everyone fishing the river even where it crosses the Crow Reservation. A full season for a non-resident is about $117.50 for 2026, with a 1-day at $31.50 and a 5-day at $73.50. The river is artificial-lures-only on the main stretch. Trout are released.

The authority and the Crow Reservation point. The licence authority is Montana Fish, Wildlife & Parks (FWP). The river runs through the Crow Reservation, and a State of Montana fishing licence is required for all anglers fishing the Bighorn within the reservation boundaries at the public access sites (Montana FWP / Central District regulations). The standard state licence covers the river itself where you fish it from the public access; you do not buy a separate tribal river permit to float and fish the main run.

A Montana licence is built from three parts. Every angler aged 12 or over needs all three (Montana FWP):

2026 non-resident fishing-licence durations (Montana FWP, via fwp.mt.gov and the Central District regulations, as of 5 June 2026). The totals below already include the $10 conservation licence and the $7.50 AIS pass:

How to get it

• Go to fwp.mt.gov (the FWP online licence system) and create an account, or use the MyFWP app.
• Buy the conservation licence, the AIS prevention pass and your fishing licence (1-day, 5-day or season, whichever fits your trip) in one go.
• Carry it (on your phone or printed) while you fish. Since 1 March 2026 Montana licences are sold online only (the over-the-counter sales at fly shops and sporting-goods stores have ended), so buy yours through fwp.mt.gov or the MyFWP app before you arrive.

The river's own rules (2026)

Montana FWP, Central Fishing District, Bighorn River:

Where to fish, and how to fish each part

Access is funnelled to the public sites because the banks are Crow Tribal and private. From the top, the Afterbay (3-Mile) and Lind (3-Mile) launches put you on the densest water; the Bighorn Fishing Access Site is the usual take-out about 13 miles (21 km) down. Most people float it by drift boat; you can wade at and around the access sites.

The river is big enough and the access tight enough that the drift boat is the natural way to fish it. You launch at the top, fish down through miles of water you could never reach on foot, and take out at the bottom. Wading is good but limited to the public ground at and around the launches. The access points (Montana FWP and NPS Bighorn Canyon):

• Afterbay (3-Mile) launch (top). The launch just below the Afterbay at Fort Smith, on the densest first stretch of river. The standard put-in, and the run from here down holds the most fish per mile. National Park Service / FWP managed.
• Lind (3-Mile) access. A second public access near the top of the float, used as a put-in or a take-out to split the river into a shorter day. National Park Service managed.
• Bighorn Fishing Access Site (bottom). The state-maintained access about 13 miles (21 km) below the Afterbay, the usual take-out for the full-day float and a wadeable bank fishery in its own right.

What the water type means for method

• Riffles and the heads of runs (broken, oxygenated water): rainbows and browns feeding on nymphs and emergers. A nymph rig under an indicator with a scud or sowbug and a smaller mayfly or midge nymph below it.
• Long, smooth runs and the slicks (the flat, glassy water): where rising fish show during a hatch. Switch to a dry fly rig and cast to the rise.
• Banks, undercuts and seams (where fast meets slow): the big browns. A streamer rig cast tight to the bank and stripped back, best in lower light and autumn.
• Side channels: smaller, intimate water that holds browns and lets you wade and pick fish off; nymph or dry depending on whether they are rising.

The two top launches share a "3-Mile" name because they sit on that famous first three miles below the Afterbay. If you only have a half day from the bank, fish around the Afterbay launch or the Bighorn Access; for the full river you want the float.

The rig to use: pick your fish, water and season

Three fly rigs cover the whole river. The nymph rig under an indicator is the everyday method and catches both trout all year. The dry fly rig is for when fish are rising to a hatch. The streamer rig is for the bigger browns, best in autumn and lower light. Each links to its own build page.

Plain version: if you are not sure, fish the nymph rig. It catches Bighorn trout day in, day out, on scuds, sowbugs and small mayfly or midge nymphs under an indicator. When you see noses in the slick water, change to the dry fly and match the hatch on the calendar strip. When you want a shot at a big brown, especially on a grey autumn day, tie on a streamer and work the banks.

This table is the core decision the trip turns on, and it lives on the cheat sheet too. Read it as: pick your fish, pick the water and the season, and it gives you the rig.

The boat: guided, float, or your own

Most people fish the Bighorn from a drift boat, and for a first trip a guided float is the standard. The Fort Smith fly shops run guided floats, supply the flies and read the daily flow and hatch for you. You can also rent a boat and shuttle, or bring your own. Rates vary by season and party, so book through the shops below.

A drift boat is what opens up the Bighorn, because the best water is strung along miles of river you cannot walk to. The Fort Smith fly shops are full-service: a guide, the drift boat, the flies, the local knowledge of the current flow and what is hatching, and a shuttle back to your vehicle. For a first visit that is the easy and the productive way in. Book directly:

• Bighorn Fly & Tackle, Fort Smith – guided floats, lodging, boat rentals, shuttles and a fully stocked fly shop on the river. bighornfly.com.
• Bighorn Trout Shop, Fort Smith – guided fly fishing, lodging, meals and a full fly shop. bighorntroutshop.com.
• Bighorn Angler, Fort Smith – guided floats, a year-round fly shop and a lodge in the heart of Fort Smith. bighornangler.com.

Rent a boat and shuttle

If you can row and read trout water, the shops rent drift boats and run shuttles between the launches so you can float it yourself. Confirm the rental rate, the shuttle and whether they want to see your experience when you book.

Bring your own

You can trailer your own drift boat or raft, launch at the Afterbay or Lind access and take out at the Bighorn Access, paying any launch fee and arranging your own shuttle. Watch the dam release: a change in flow changes the river fast, so check the current cfs with the shops before you put on.

Where to stay (and buy a licence locally)

Stay in Fort Smith, right on the river, where the fly shops run lodges with rooms and meals so you can sleep, eat and launch in one place. There is also lodging and camping nearby and rooms in Hardin, about 40 miles (64 km) north. Buy your Montana licence online before you arrive (since 1 March 2026 the fly shops no longer sell licences over the counter).

Stay near the water

• The Fort Smith fly-shop lodges – Bighorn Fly & Tackle, the Bighorn Trout Shop and the Bighorn Angler all run lodges with rooms, and most offer package trips that bundle lodging, meals and guided floats from the evening you arrive. The simplest way to stay on the river and fish it.
• Fort Smith itself is a small fishing village built around the river, with the shops, lodging and the launches all together.
• Hardin, about 40 miles (64 km) north on the I-90 corridor, has motels and services if Fort Smith is full or you want a town base.

Buy a licence online at fwp.mt.gov or on the MyFWP app before you arrive. Since 1 March 2026 Montana has ended over-the-counter licence sales at fly shops and sporting-goods stores, so sort it out before you reach Fort Smith.

Build your kit (the kit builder and the shopping list)

Pick your method (nymph, dry or streamer) and the kit builder trims the shopping list and the rigs to exactly what you need. One 9 ft 5-weight fly outfit fishes the whole river; you change the leader, the tippet and the flies for the three methods. The full list is below, grouped, with no brands and no prices.

That is the whole list. One 9 ft 5-weight outfit, a floating line, a couple of leaders and three or four tippet spools, a small box each of scuds and sowbugs, midges, mayflies, caddis and streamers, and your waders and net. You do not need a named brand to catch a Bighorn trout; buy generic sizes and the right patterns.

A trip checklist

Before you go: check your dates against the hatches and the current flow, buy the Montana licence (conservation licence, AIS pass and fishing licence), decide float or wade and book a guide or boat through a Fort Smith shop, pack the one fly outfit and the Bighorn fly boxes, and note that it is artificial-only and release. Then print the cheat sheet and take it with you.

Do this in order:

1. Check your dates and the flow. Match your trip to the hatch you want on the calendar strip above (June to September for peak dry fly, autumn for streamers, winter for midges), and check the current dam release and fishing report with a Fort Smith fly shop before you commit.
2. Buy the Montana licence. Online at fwp.mt.gov or the MyFWP app: the conservation licence, the AIS prevention pass and your fishing licence (1-day, 5-day or season). Carry it while you fish, including on the reservation stretch.
3. Decide float or wade, and book it. For a first trip, book a guided float through a Fort Smith shop (Bighorn Fly & Tackle, Bighorn Trout Shop or Bighorn Angler). To do it yourself, arrange a boat rental and shuttle, or bring your own and plan the put-in and take-out.
4. Pack the one outfit and the boxes. A 9 ft 5-weight, a floating line, leaders and tippet, and the scud/sowbug, midge, mayfly, caddis and streamer boxes. The shopping list above (trimmed by the kit builder) is your packing list. Waders, a rubber net, polarised glasses and rain layers.
5. Note the rules. Artificial lures only on the main stretch, the standard trout limit, and release as the norm. Pinch your barbs, keep fish in the water, and clean and dry your kit between rivers.
6. Print the cheat sheet and fold it into the box. Get the printable cheat sheet

Common mistakes

The big ones: ignoring the dam release and turning up to the wrong flow, fishing too heavy a tippet in this clear water, missing the artificial-only rule, fishing the bright middle of a summer day, and trying to wade water that wants a boat. None is hard to avoid once you know.

• Ignoring the flow. The dam sets the river. A high release pushes fish to the banks and makes wading hard; a low, clear release concentrates them. Check the current cfs and the report with a Fort Smith shop before you go, and plan the day around it.
• Fishing too heavy. The Bighorn is cold and clear and the trout see a lot of anglers, so they can be fussy. Drop to 5X or 6X tippet and small flies when they are picky, especially in the slicks and on the trico.
• Missing the artificial-only rule. From just below the Afterbay down to the Bighorn Access it is artificial lures only, no bait. Plan to fish flies; do not turn up expecting to fish a worm.
• Fishing the bright middle of a summer day. In high summer the best windows are the morning trico spinner fall and the evening caddis. The glaring midday is slow. Fish early and late and rest in between.
• Trying to wade what wants a boat. The banks are largely Crow Tribal and private, and the best water is strung along miles of river. Wade around the access sites, but float the river to fish it properly.
• Skipping the AIS pass, or not cleaning your kit. The AIS prevention pass is part of every Montana licence, and cleaning and drying your boots and net between rivers is both the rule's intent and good practice. Do both.

Frequently asked questions

The questions travelling anglers ask most about the Bighorn: what is here, the Montana licence and the Crow Reservation point, prices, the best time, bank versus boat, the access sites, the flies, keeping fish, the artificial-only rule, and the one outfit.