Montana Fly Fishing 6 min read

DIY Guide to Fly Fishing the Clark Fork River in Montana

Ken Sperry

Posted by Ken Sperry

March 9, 2024

The massive Clark Fork watershed comprises over 14 million acres, with its vast network of streams and rivers cascading and meandering for over 28,000 miles through the rugged, mountainous landscape of western Montana.

This hard-working watershed supports an intricately woven ecosystem of plants and wildlife in its upper reaches; steep slopes of dense, mixed coniferous forest line the banks of cold, clear streams, with Montana’s native westslope cutthroat trout and wild brown and rainbow trout holding in almost every lie.

Fly Fishing Montana’s Clark Fork River for Cutthroat Trout

Nature has an innate ability to heal itself despite humans’ attempts to destroy it. Please don’t misunderstand; this will not be a political dissertation. We love fishing, in particular fly fishing. Before you schedule your fishing vacation to the great state of Montana to tackle the Clark Fork River, you should have a basic understanding of the miracle that is the home to rainbows and browns.

Over a century ago, a copper boom occurred in this region. Hundreds of mines were dug, and then, in 1908, a flood occurred, which washed contamination into the Clark Fork River. These toxins spilled into the river and its banks, contaminating over 120 miles of this river. This was when the trout population disappeared.

Thankfully, in a twist of irony, arsenic was discovered in the 1980s Milltown drinking water. This spearheaded the river’s clean-up, which is why we can enjoy the Clark Fork River today.

Clark Fork River Map, Fishing Access Sites, and Boat Launches

Map of fishing access spots on the Clark Fork River in Montana

Get directions to fishing access points and real-time stream flow data with the DIY Fly Fishing Map

What to Expect on the Clark Fork

The Clark’s location is simple to describe. Just look for I-90 on a map in Montana. The Clark parallels this interstate. The section we will focus on runs from Clinton to Missoula, where Rock Creek, Blackfoot River, and Bitterroot River intersect with the Clark. This is one of the longest rivers in Montana, so bear in mind that fishing opportunities are not limited to this section.

The river’s width, depth, and neighboring land characteristics vary greatly throughout its long journey. The section from Clinton to Missoula flows through mountainous terrain. Forests grow on the sides and tops of mountains and right on the river’s edge.

In other sections, the Clark takes on a short width and depth. Between Clinton and Missoula, it becomes wider and deeper. Wading becomes practically impossible, except for the shallower portions. You will find them here if you enjoy fly fishing riffles and runs.

The water temperatures run cooler at the Rock Creek and Blackfoot River’s intersections. This is prime water conditions for rainbow and brown trout and cutthroats.

Clark Fork River Tributaries

Numerous tributaries to the Clark Fork River also provide excellent trout fishing opportunities. A few to consider are listed below.

Major Tributaries

Minor Tributaries

Best Places to Fish the Clark Fork River

Access to the Clark Fork River from Clinton to Missoula is good. There is a good selection of public access points and a complement of bridge crossings. These bridge crossings offer the angler “off the books” access points, which are considered to be informal.

For the fly fishing anglers who don’t mind a trek, an abandoned railroad follows this river at various locations. By following these stretches, anglers can reach parts of the Clark for practical isolation from mankind. However, this comes at a risk. The risk is trespassing. While there is some question about land ownership along this abandoned railroad, bear this in mind if you adventure along it.

There are numerous stretches of the Clark where wade fishing is the preferred, if not the only, way to tackle the river. This is where the width and depth are conducive to this type of angling, as there are some stretches where the width is a mere 10-15 feet across.

This is not the case, for the most part, from Clinton to Missoula. As this section grows in width and depth, wading across the river (as previously mentioned) is impossible except for the shallower portions. If you float this section, use caution and check with the local authorities before departing.

For example, the Clark splits into two channels in Missoula. It is suggested that floaters, as of this writing, use the left channel to avoid a dam and portage.

Clark Fork River Flow and Current Conditions

Clark Fork below Missoula MT

  • Streamflow: 7270 ft³/s
  • Gage height: 3.71 ft
Streamflow GraphGage height Graph

Best Time to Fish the Clark Fork River

The best time to fish the Clark Fork River in Montana depends on what kind of fishing experience you’re looking for:

  • Spring (March-May): This can be an excellent time to fish for big brown trout with streamers, especially on the upper Clark Fork. However, water conditions can change daily due to runoff. The lower Clark Fork is a better option during this time, with hatches of Blue-Winged Olives and Skwalas.
  • Summer (June-August): The upper Clark Fork fishes well for Caddis and terrestrial insects throughout the summer. There are also isolated stonefly hatches below the confluence with Rock Creek. The lower Clark Fork stays cooler than other rivers in the summer heat, so it can be a good option in July and August.
  • Fall (September-November): Many anglers consider this the prime time for fly fishing on the Clark Fork. The hatches change from hoppers and Tricos to Blue-Winged Olives and Mahoganies, and the longer, slower pools hold pods of feeding trout. Streamer fishing also picks up again in the fall.

Clark Fork Hatches

There are two major hatches worth considering. The first is the Salmonfly hatch, which begins late in the month of May. When considering fly fishing, it is important to note that spring runoff may cloud the water. If this is the case, your fishing trip will not have much “catching.” However, the river can run clear during this hatch, and the fishing is amazing with the clear water conditions.

The other major hatch is noteworthy from the middle of June through July. This is when the Green and Brown Drake hatch gets going. Yet again, this will depend on the spring runoff, as water conditions can be favorable or unfavorable.

Other fly fishing opportunities are available on the Clark. Mid-July through September offers anglers hopper fishing. Additionally, the fall months offer the opportunity to catch nice-sized rainbows and browns while streamer fishing.

Best Flies for the Clark Fork River

The flies you will want to use are predicated on the time of year your trip is scheduled. Let’s start with the Salmonfly hatch. If the water is clear, sizes 2-6 of the Kaufmanns Stone and Brooks Stone consistently bring in great results.

For the Green and Brown Drake hatch from the middle of June through July, a couple of reliable options exist to attract the brown and rainbow trout. For dry fly fishing, tie on sizes 12-16 of the Olive Sparkle Dun or Green Drake Emerger. A size 12-16 of the Hare’s Ear Nymph has yielded successful results for nymph fans.

If you enjoy this section of the Clark Fork River between late June and July, you can also try Stonefly Imitations. The Montana Nymph and Golden Stone Nymph, in sizes 4-10, have brought anglers good-sized trout.

Hopper fishing is something that every angler should experience. From mid-July through September, standard hopper imitations in sizes 4-10 have brought in good-sized trout.

Streamers have attracted many large brown and rainbow trout during the fall months. Toss them in holes, as well as other areas that are conducive to trout habitat.

Gear Recommendations

A 9-foot 5-wt fly rod with a floating line is perfect for fishing dry flies and small nymphs on the Clark Fork River. A 9-foot 6-wt with a sink tip fly line for larger nymphs and streamers makes life easier. A tapered 9-foot leader, with tippet size 3X to 6X to match the flies you are throwing, is pretty standard.

Clark Fork River Fishing Reports

Several area fly shops and online retailers publish Clark Fork River fishing reports. Below are a few to check out.

Clark Fork River Fishing Regulations

One of the necessary “evils,” if you will, of traveling to another state for a fishing vacation is purchasing an out-of-state fishing license. The Montana Fish, Wildlife, & Parks has a user-friendly website to assist anglers in “getting legal” before the trip.

Clark Fork River Trip Planning Tips

Traveling to this portion of Montana is easier than traveling to the more remote locations of other rivers. It bears repeating that the Clark runs parallel, in essence, to I-90. Several portions of the river are so close to I-90 that anglers and recreational enthusiasts can hear the interstate traffic.

The city of Missoula has an international airport. This airport has been undergoing renovations and expansions, so checking airfare flying directly into this city would be worthwhile. Missoula is close to a 5 ½ hour drive from Billings, where Billings Logan International Airport is. This is Montana’s major airline travel hub and often is where the cheapest airline fare can be found.

Lodging will not be challenging, as there are various options in Missoula. Since this section is approximately 20 miles long, travel to and from the Clark will be short.

Looking for more places to fish in Montana? Check our DIY Guide to the Best Fly Fishing in Montana

Feature image by Sooter