The Firehole is quite possibly the most unique trout river in the world. It flows through three of the largest and most active geyser basins in the world, including iconic thermal features such as Old Faithful and Grand Prismatic spring. The outflow from these features flow directly into the river and you will have to dodge mud pots and hot springs as you walk along the banks. Wildlife is plentiful in the area, with frequent sightings of elk, bison and bear. The Firehole would be a worthwhile destination without even wetting a line, but fortunately for anglers the river boasts a prolific population of both trout and insects.
Fishing Overview- Species and Seasons
Both Brown and Rainbow Trout are present in good numbers throughout the river, with Brook Trout being found in the far headwater reaches. The Firehole is not known as a big fish river, with the average trout running from 8-12 inches. However, the fish are plentiful, feisty, and eager to eat flies. I have taken fish of up to 18 inches in the river, but fish over 15” are not common.
Because the Firehole is heavily influenced by thermally heated water, it behaves differently than your typical Rocky Mountain trout stream. It produces excellent fishing early and late in the season but becomes too warm during the hot summer months. Yellowstone Park opens to fishing on Memorial Day weekend and the Firehole will fish from the get go. It will sometimes be high and tea colored, but I have never seen the river too muddy to fish. Consistent dry fly fishing can happen right away, but after high snow years can take a week or 10 days to really get cranking. Afternoon fishing slows down in late June as water temps rise and shuts down completely sometime in early July. Water temps of over 80 degrees are possible and the river should not be fished over about 72 degrees. Fishing begins again with the first cold snap in September and continues to be strong through the closure of Yellowstone Park the first weekend in November.
Sections and Access
From the anglers’ perspective, the Firehole can be broken down into 3 distinct sections. The first section is the rivers headwaters above (south of) Old Faithful. This section contains a good number of small brook trout. While it is a fun place to fish, it would not be considered a destination for visiting anglers. The section of river through Upper Geyser Basin is closed to fishing. The river re-opens to fishing downstream where it runs under the Grand Loop Road at Biscuit Basin, approximately 2 miles north of Old Faithful. The next 10 miles of river, down to Firehole Falls, offer the best and most consistent fishing on the river. In this stretch the river is often visible from the road and there are numerous pull-offs and parking areas that provide access. I compare the river in this stretch to a large spring creek. Aquatic weeds are abundant and there are many long, slick glides where trout will often be found rising. Long, choppy riffles also provide ideal habitat and easier to approach fish. At Firehole Falls, the river makes a dramatic change in character as a plunges into a deep canyon. There is only about a mile of fishable water below the falls before the Firehole meets the Gibbon to form the world famous Madison River. However, this stretch of river is important to anglers for two reasons. First, migrating fish from Hebgen Lake have access to this stretch, giving the angler a chance for a large trout. Second, this reach of water has a salmonfly hatch which, due to the thermal heating, is one of the earliest in the region. This section of river is accessed via the one-way Firehole Falls Drive, which branches off the main road just south of Madison Junction.
Hatches and Dry Flies
One of biggest draws of the Firehole is the dry fly fishing. Because of the incredible diversity of insect life in the river from Biscuit Basin to Firehole Falls, actively rising fish are a common sight. The first hatches of the year will be midges and Blue Winged Olives. A simple Parachute Adams in the appropriate size covers this just fine. You can usually get away with 4x tippet but you should have 5x just in case. I like a 4wt rod due to the size of the fish but a 5wt works just fine. One thing I like to do when fishing any hatch is to fish an emerger pattern as a dropper behind my dry fly. I like to grease up the emerger so that it floats in the film, just barely under the surface of the water.
As the weather warms sometime in early June, Pale Morning Duns begin to appear but the Caddis hatch quickly becomes the bug du jour for the trout. While there are numerous species of caddis present, the Nectopsyche, commonly known as the White Miller, is the most important. This is a large, light cream colored bug that entices vicious, splashy rises from the trout. The flies used to match this hatch are usually a #10 so they float well and are easy to see, a huge bonus for the angler. This is not a common caddis species in many parts to the country, so it is wise to visit a local fly shop to check out their selection of White Miller Patterns. It is also wise to carry some smaller, darker patterns just in case so bring some of your favorites in a #14 olive. A small black caddis in a #18 can also be seen on the river at times. For the Pale Morning Duns, I prefer a cripple pattern but duns are also effective, #16 and #18. As always, carry the appropriate emergers to fish behind your dry fly.
In the fall, the same menu of hatches (minus the PMD’s) is available, just in the reverse order. The caddis will get going again with cool weather in September and gradually give way to BWO’s and midges as nasty, snowy weather hits in October. In the fall, the water is lower and the fish are more educated, so be prepared to fish smaller and lighter than you did in the spring. Spring and fall, be prepared to fish all of these hatches on any given day. Given the elevated water temperatures in the river, all it takes is a change in temperature or cloud cover to change the predominant bug on the water.
In the Firehole Canyon, the Salmonfly hatch is usually off and running by the first week of June. Since the fish are generally small, you may want to downsize your salmonfly a bit. If you are still missing too many fish then you can always go to a general attracter such as a PMX or Turk’s Tarantula in a smaller size. There can be the occasional surprise from Hebgen Lake or the Madison in this section of river.
Swinging Soft Hackles
One sight you will rarely see on the Firehole is a strike indicator. During high water or lulls in hatches you will find most anglers on the river swinging wet flies or soft hackles in the traditional down and across method. This centuries old technique from the British Isles has fallen out of favor with many anglers but is a fun and effective way to fish. The swinging motion of the fly imitates an emerging insect that is swimming towards to surface in an effort to hatch. The trout will hit your fly on the run so you will feel the tug.
This method of fishing is most effective in the riffles. I look for the knee to waist deep choppy water of medium speed. You want to position yourself at the top of the riffle and gradually fish your way downstream. Your cast should be across the current towards the far bank and slightly downstream of your position. You want to hold your line tight and follow the fly as it swings across the riffle. Once the fly comes to a complete stop below you, I like to let it hang for a few seconds before I begin to strip it back to me. When a trout strikes, you simply raise your rod tip, they are essentially hooking themselves. You will always miss some fish with this method but once you get the hang of it can be deadly effective. For flies, it is a hard to beat a Beadhead Soft Hackle Pheasant Tail in a size 12 or 14. Other patterns such as a SH Hare’s Ear and SH Copper John work great as well.