The 2025 Bighorn River Fly-Fishing Season

A Season Recap Provided by Steve Galletta & Hale Harris

The 2025 fly fishing season on Montana’s Bighorn River will be remembered as a year of contrasts — one defined by low flows, cold water temperatures, and challenging hatches, yet also by some of the largest trout the river has produced in recent memory. Despite inconsistent insect activity and persistent algae issues early in the season, anglers who adapted to conditions found exceptional fishing, particularly with nymphs and later during the impressive black caddis emergence. 

Steve Galletta with a healthy brown trout. Large trout of both species made the 2025 particularly memorable.

Low Water and Colder-than-Normal Conditions

From the season’s start, it was clear that 2025 would not be a typical year on the Bighorn. Low inflows into Yellowtail Reservoir during the winter and early spring led to reduced releases, keeping the river at lower-than-average flows. These conditions created a smaller river channel, with exposed gravel bars and slower current seams, making fish more concentrated but also more cautious. Compounding the low water, the releases from the dam were colder than usual — a result of extended snowpack in the high country and the operators drawing from deeper, chillier layers of the reservoir.

While cold water typically benefits trout by increasing oxygen levels and slowing metabolism, it also delayed the progression of aquatic insect life. Early-season anglers noticed that the river’s normally reliable Baetis mayfly hatch was underwhelming. Instead of the thick, consistent blue-winged olive emergences that usually bring pods of rising trout to the surface in April and early May, this year’s hatch was sporadic and thin. Many days passed without significant surface activity, leaving dry fly enthusiasts searching for other options.

Algae and the Short-Lived Pale Morning Dun Hatch

As spring gave way to early summer, a different challenge emerged — algae. Low, cold water limited the river’s flushing capacity, allowing filamentous algae to accumulate across many of the classic riffles and runs between the Afterbay and Bighorn accesses. For a time, anglers found themselves cleaning flies and lines more often than they’d like, especially those fishing nymph rigs near the bottom. Fortunately, by midsummer the algae problem began to subside as the river warmed slightly and natural die-off occurred.

When the Pale Morning Duns finally appeared in late June, they brought welcome relief. Though the hatch was short-lived compared to previous years, it still produced several weeks of excellent dry fly fishing. For many anglers, those calm mornings and soft summer evenings filled with the delicate rise forms of trout sipping PMDs were the season’s first true moments of classic Bighorn magic. The hatch may not have lasted long, but it offered a glimpse of the river’s enduring vitality.

Nymphing Dominates and Trophy Fish Abound

Throughout the year, nymph fishing carried the Bighorn. Despite unpredictable hatches, subsurface activity remained consistently strong. The combination of abundant scuds, sowbugs, and midge larvae kept trout feeding heavily beneath the surface. Anglers who adjusted depth, weight, and drift found outstanding success. Standard patterns — orange and tan scuds, Ray Charles sowbugs, zebra midges, and small perdigons — all produced steady hookups.

Perhaps the most remarkable story of 2025 was not the quantity of fish caught, but their size. Reports of personal-best trout came in from nearly every reach of the river. Browns pushing 22 to 24 inches and rainbows approaching similar dimensions were not uncommon. Guides speculated that the combination of reduced angling pressure in the early season, abundant food, and cool, oxygen-rich water allowed trout to grow thicker and stronger than in recent years. These large, well-conditioned fish reminded everyone why the Bighorn remains one of the West’s premier tailwater fisheries.

The Season of the Black Caddis

If one hatch redeemed the year, it was the black caddis. Beginning in mid-July and

extending well into August, the river exploded with life each afternoon as millions of small, dark-bodied caddis emerged from riffles and seams. This hatch provided the best dry fly fishing of the year — perhaps of the last several seasons. Trout rose aggressively to skittering caddis adults, and anglers experienced explosive surface takes in the fading light. For many, those evenings defined the 2025 season. The low water, which had been a challenge earlier in the year, actually enhanced this event, concentrating trout into predictable lanes and making for exhilarating sight-fishing.

A Season of Manageable Grass and Clear Water

Interestingly, aquatic grass — often a late-summer nuisance on the Bighorn — was not a significant issue this year. The combination of cool, steady water temperatures and limited nutrient buildup prevented the dense mats of grass that can sometimes complicate presentations in August and September. Anglers enjoyed clear drifts and clean hooksets throughout much of the late season, further contributing to the strong fishing conditions.

Lake Turnover and the Promise of Fall Streamers

As October approached, the dynamic of the river began to shift once again. Just a week ago, Yellowtail Reservoir completed its seasonal turnover — a process that mixes the lake’s stratified layers, temporarily clouding the river with suspended sediment and organic matter. While this reduced visibility, it did little to dampen the trout’s appetite. In fact, many seasoned Bighorn anglers look forward to this period, when aggressive browns and rainbows respond to larger patterns and the promise of fall streamer action looms large.

With cooling temperatures and the onset of spawning behavior, streamer fishing is set to become the “main event” as fall progresses. Big articulated patterns in natural tones, swung through deeper runs or stripped along banks, are already producing impressive fish. Given the size and condition of this year’s trout, the late-season bite could be extraordinary.

Conclusion

The 2025 Bighorn River fly fishing season was not without its frustrations — the weak Baetis hatch, persistent algae, and short PMD run tested anglers’ patience. Yet, those who adapted to the rhythm of the river found immense reward. Exceptional fish size, world-class nymphing, and a spectacular black caddis emergence defined the heart of the season. Even now, as the river adjusts to lake turnover and prepares for the chill of winter, it continues to fish well. In a year of low water and cold flows, the Bighorn once again proved its resilience — and reminded all who fished it that this river, no matter the conditions, remains one of the finest trout streams in the world.