Montana Fly Fishing
The Bighorn River

Bighorn River

Fly Fishing the Bighorn River

Afterbay Reservoir at Sunset
Photo Use Guidelines

The Bighorn River is considered to be one of the finest trout streams not just in Montana but in the lower forty-eight states. The river consistently pulls out large fish. Brown trout average about 15 inches, while rainbow trout average around 16 inches. The river has outstanding hatches. And unlike many rivers in Montana, the Bighorn is a high quality fly fishing river for the entire year, offering anglers who don't mind the elements the opportunity to catch large fish in the middle of the winter.

Trout fishing on the Bighorn River is generally localized to the first 13 miles below the dam, to the Bighorn Access Site. In these upper thirteen miles, Afterbay Dam regulates river flows and irrigation has only a minimal impact on river flows. As a result, the Bighorn River almost always flows steady, clear and cool, creating ideal fishing conditions.

Below Bighorn Access Site, the current begins to slow down somewhat and becomes quite slow as it nears the Yellowstone River. Irrigation also begins to pull water out of the Bighorn. As a result, the temperature of the Bighorn River begins to warm up. Good trout fishing, particularly for brown trout, can be had between the Bighorn Access Site and the Two Leggins Access Site, although the numbers of trout per mile are less than found further upstream. Below Two Leggins all the way down to the Yellowstone River, large brown trout can still be found although their numbers are quite low. Generally, except during the fall and spring, the lower half of the Bighorn River is a warm water fishery for catfish, whitefish and bass.

Bighorn River below Afterbay Dam in Montana
Photo Use Guidelines

Not surprisingly, the upper 13 miles of the Bighorn River have exceptionally heavy fly fishing pressure. The period between July and September sees the heaviest use. On a busy summer day, it is not uncommon to see dozens of rafts floating the river with many more anglers fly fishing from the rivers banks.

Once the busy season of summer passes, fly fishing pressure does reduce. However, even during the dead of winter, the river still sees fairly consistent use as the river as anglers come from all over to take advantage of the quality fishing the Bighorn River provides during the winter.

Any angler visiting the Bighorn River in winter (November - March) should come prepared. Being located on the western edge of the high plains can provide for wild shifts in weather. Some days will be in the sixties, while others will have sub-zero temperatures with blizzard conditions. So the motto for winter fly fishing in the Bighorn River is to come prepared for truly anything.

In general, the Bighorn River fishes well for both wade anglers and floaters, although wade anglers may have problems during higher water. Additionally, floaters have the big advantage of being able to easily go from prime location to another, as well as being easily able to cover the whole width of the river.

Bighorn River : Afterbay Dam to Bighorn Access Site

As mentioned, the best fishing is found on this stretch - or the upper 13 miles of the river right below the dam. Estimates put the fish populations on this stretch between 3000-5000 fish per mile, with a significant proportion of the fish well over fourteen inches. The rich fertility of the Bighorn River on this section allows trout to grow very quickly.

During the winter, midges are the flies of choice. They are best fished in a dead drift in slower water, not out in fast current. Fishing the midges in deep water is also important. The depth of the drift should either be right along the bottom or near the surface of the river. Suggested patterns are the standard Adams, Serendipity and Griffiths Gnat, sized 18-24, used on long, light leaders. For anglers who like using them, San Juan Worms, which imitate the red worms found in the river, are also an excellent choice. It is also worth remembering that fishing midges and San Juan Worms on the Bighorn River generally work well all year. So don't be bashful about using midges and worms during the summer if the standard patterns and techniques aren't working.

Bighorn River at Mallards Landing
Photo Use Guidelines

Beginning in April and usually lasting until early June, a blue-winged olive hatch occurs. These hatches usually occur during mid-day, with the heaviest part occurring in mid-afternoon when the temperature is at its warmest. Both dry flies and nymphs can be successfully used during this hatch. For the dry fly angler, the Parachute Adams, in smaller sizes, works very well. Popular nymph flies include the Pheasant Tail Nymph and Hare's Ear Nymph, in sizes 16-20.

July on the river sees the little yellow stonefly hatch. Fishing the yellow stonefly hatch can provide the angler with solid fishing. Additionally, fishing is somewhat easier during early July than later in the month as the hordes of anglers have yet to arrive. Best of all, fishing the yellow stonefly hatch requires less precision on the parts of anglers. A popular approach to fishing during this hatch is to use a Elk Hair Caddis or Stimulator in sizes 16-18, throwing them out into the heavier current and riffles.

Late summer on the Bighorn River sees its most prolific and most heavily fished hatches. Starting later in July and lasting through the middle of August, excellent pale morning dun hatches occur. The PMD hatch generally occurs during the middle of the day. Standard dry fly patterns, such as the Sparkle Dun and PMD Cripple, sizes 14-18, work well. When dry fly fishing, it is vitally important to have a drag free drift. The trout in the Bighorn River have lots of artificial flies thrown at them over the course of the year, and will not be impressed by a dry fly that leaves a little wake behind it.

When fly fishing nymphs during the PMD hatch, the best technique is to dead drift the nymph in faster water, particularly in the riffles. A light colored Hare's Ear nymph, sized 16-20, is a popular nymph pattern used during the PMD hatch.

Perhaps the best fly fishing on the Bighorn River occurs during August, although there are some slow days. During August, the PMD hatch is just beginning to end, while the caddis hatch is just beginning. The caddis hatch usually begins in mid-August and can last well into September. The heaviest hatch generally occurs in the evening. Popular flies used during the caddis hatch include the standby Elk Hair Caddis, the Tan Caddis as well as the X-Caddis, in sizes 14-18.

Fall on the river sees a solid trico hatch. The tricos come off the water in the evenings and return in the early morning, where they lay their eggs. These hatches are easily located by looking for swarms of these tiny flies hovering above the river. Despite the tiny sizes of these flies, large trout, especially large rainbows, come up to feed on them, providing a real challenge for an angler who manages to find one considering the light tackle that must be used. Popular patterns to use during the Trico hatch are a parachute Trico and a parachute Adams, in small sizes of 20-24, with very light tippets (6x or 7x are standard).

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