Boulder River Float Fishing Trips

Boulder River Float Fishing Trips

At Parks’ Fly Shop, we mostly float the Yellowstone River. We do offer Montana float fishing trips on three other rivers, though: the Lower Madison, Boulder, and Stillwater Rivers. The Lower Madison is our go-to float river in late May and June when the Yellowstone is muddy, Boulder River float fishing trips are possible in early May, June, and July, and the Stillwater is a great option from July into September and sometimes through the fall. In this next series of blog posts, Walter will discuss our float fishing trips on these rivers. First up is the Boulder. Visit this page for more information on our float trips.

angler with boulder river brown trout
Solid brown trout from the Boulder River in early July 2020. This fish ate a Lex’s Golden Stonefly Nymph, one of the top flies on Boulder River float fishing trips.

Introduction to Boulder River Float Fishing Trips

  • Season: Late April and Early May before the spring runoff hits, during short “runoff breaks” in May and June, and in July until flows drop to about 500cfs.
  • The Fishing: Fast-paced nymph and dry-dropper fishing from the boat, with some match the hatch opportunities in July both on foot and from the raft.
  • The Fish: Rainbow and brown trout averaging 8 to 16 inches but occasionally flirting with 20 inches, plus abundant and very large whitefish in the deep pools.
  • The Boat: Because the Boulder is shallow and rocky and many of its accesses are rough, all float fishing trips on the Boulder River utilize rafts.

Our Boulder River float fishing trips take place in the lower portion of the river below Natural Bridge Falls Recreation Area. This 20-odd mile stretch of river allows for two different full-day floats as well as a short section suitable for a half-day float provided we get out and do some walk-wade fishing as well. There are five float fishing access points on the river, plus the Otter takeout on the Yellowstone where some lower Boulder River float fishing trips take out.

Almost all sections of the Boulder are small, steep, fast, and bouldery. This makes accurate casting critical and makes the fishing very fast-paced. For this reason, it’s a poor choice for beginner and novice clients. It’s great for clients who can hit their spots and like fishing for numerous and healthy midsized trout that fight above their weight, with opportunities for a few solid but not enormous fish mixed in.

The Boulder River is located south of Big Timber, Montana, with most Boulder River float fishing trips starting around one hour from Livingston, Montana. This makes the float portions of the Boulder around 1hr 45min travel time from Gardiner.

Introduction to the Boulder River

The Boulder River and its numerous tributaries and forks rise north of Yellowstone ParkĀ  in the northwest Absaroka Mountains. The forks all come together near McLeod, Montana, then the Boulder flows north to join the Yellowstone near Big Timber. While good fishing exists on the upper Boulder in the Custer-Gallatin National Forest upstream from Natural Bridge Falls Recreation Area (a fantasic side trip where the river briefly flows underground before jetting from a cliff face as a tall waterfall), float fishing is impossible in the headwaters because of the river’s small size and numerous intense rapids.

Downstream of Natural Bridge, the Boulder slows and flows in numerous undercut bends resembling the Lamar River. Unfortunately, this section of river is located entirely on private land and the waterfall upstream makes it impossible to access.

At the East Boulder Road Bridge, flows begin to increase again and the river gains volume from the East Boulder River. Boulder River float fishing trips begin here and continue to the Boulder’s confluence with the Yellowstone. This upper portion is smaller and slower than lower portions, so it’s excellent for getting out and wade fishing.

At Boulder Forks near McLeod, the West Boulder joins and the river gets steep and fast again. It remains steep and fast all the way to the Yellowstone and public access is limited to bridges and small access points, so float-fishing is the best option. For the remainder of the trip to the Yellowstone, the Boulder is almost continuous class-I and class-II whitewater, with a few class-III waves thrown in when trees fall into the river and around nasty islands. While there are a few big pools and riffle corners that invite wade-fishing, for the most part the river flows fast over a bed choked in large boulders, each one of which invites a cast or two as the raft blows by.

image showing angler fishing the boulder river
Walter wade-fishing a riffle corner on the Boulder. We often get out to fish spots like this on foot, especially when the water is quite high or quite low and the fish tend to stack in the larger pools.

Speaking of rafts, all Boulder River float fishing trips require one. The river is far too shallow and rocky for drift boats to survive the trip, even when the water is high.

Unlike most rivers in the area, the Boulder never really gets too muddy to fish during the spring snowmelt. It does get too high. This occurs about a week after the Yellowstone blows out, usually between May 10 and 20. Even during the spring melt, short windows of good fishing occur during cooldowns that allow the river to drop. Most rivers in the region can fish well when the water is up in the bankside bushes. The Boulder can fish well when the river is up in the trees. Still, flows need to be under about 2700 cubic feet per second for floating to be safe. Even then, it’s important to watch out for recently-dropped trees in the river.

The Boulder really kicks into gear in an average year around June 25 to July 1, when flows drop below about 1500cfs and the fish begin eating dry flies. Prime flows continue until the river hits about 800cfs.

Though the fishing and especially the floating get more difficult once flows drop under 800, Boulder River float fishing trips continue until flows drop to a bit over 500cfs, with the section between the East Boulder Bridge and Boulder Forks and the section between the 8-Mile Bridge south of Big Timber and a takeout at a city park in Big Timber remaining floatable the longest. In a year that sees normal snowpack and summer precipitation, this usually occurs between July 20 and August 1.

Fishing the Boulder River

During the brief periods when Boulder River float fishing trips are possible during the high water of May and June, most fishing is with deep nymph rigs. When nymphing the Boulder, we almost always use a stonefly nymph with a smaller nymph on the dropper. Girdle Bugs, the “Bomb Series” nymphs, and Lex’s Golden Stones are our bread and butter stoneflies, while Iron Sallies, Princes, and assorted caddis pupae are good droppers. Because the river is full of snags, we like jig-style nymphs here. During the early season, we nymph-fish from the raft, but also get out and wade the best pools. During high water, we’ll often catch the majority of our trout from the pools.

Streamer fishing can also be quite good early on, especially when the water’s on the drop in late June. No need to get fancy here: medium-sized Woolly Buggers and Sparkle Minnows are usually the best flies. On Boulder River float fishing trips there’s no need for long sink-tips. A short poly leader is fine. Casts do need to be accurate, though.

The big draw on Boulder River float fishing trips is the July dry-dropper and dry fly fishing. Most fishing is dry-dropper. Sometimes we’ll go huge, with a #6-8 Chubby Chernobyl trailing a medium-sized Girdle Bug or similar generic stonefly nymph. The TJ Hooker is a great stonefly-streamer combo that works great under a Girdle Bug, since it works even when the guide has to dodge rocks or the clients have to twitch the nymph to keep it from hanging up in shallow spots. Learn to tie it here.

When the giant Chubby Chernobyl is too big, a slightly smaller attractor like a #10 Synth Double Wing, #12 Trude, smaller Chubby Chernobyl, or #10 Turck’s Tarantula is a good bet. We’ll trail these with caddis pupae, Prince nymphs, or the Iron Sally.

While the Boulder doesn’t have wall-to-wall hatches, most Boulder River float fishing trips in July will see the fish keying on emerging aquatic insects for at least a while each days. During the day, we see PMDs and Yellow Sally stoneflies. In late afternoon, tan caddis often hatch, especially when it’s cloudy. Because the river is so fast and turbulent, specialty hatch-matching dry flies designed to float well and be visible are required. Our favorite PMD on the Boulder is Galloups’ Found Link PMD, for example, even though we don’t use it a lot elsewhere. During hatches, we’ll usually fish a smaller Clacka Caddis or Trude attractor dry trailing the appropriate hatch-matcher.

Regardless of technique, most fishing when flows are from 1500 down to 800cfs will be from the boat, since these are prime levels for the fish to be scattered through the river. Once flows drop below 800cfs, we’ll start hopping out to wade-fish the deeper areas, since the river by this point is getting low enough that the fish are starting to move out of the long, shallow runs.

Flows getting too low for Boulder River float fishing trips? Not a problem! We also run wade-fishing trips on the East and West Boulder, which are small streams, and on the mainstem of the Boulder itself. These trips are best-suited to anglers either staying in Livingston or on their way headed eastward, because they’re really too far from Gardiner for Gardiner to make sense as a home base. That said, wade fishing trips in the Boulder Drainage are often MUCH less crowded than trips in Yellowstone Park, since this area is a bit off the beaten path. If you’re looking for a float trip once the Boulder gets too low, the Stillwater River is the Boulder’s “big sister” and fishes for at least six weeks later into the season. Watch the blog for my post introducing the Stillwater, which should come up in a couple weeks.

female angler with large boulder river brown trout

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