Fall brown trout push builds on Yellowstone and Missouri tributaries

What's biting

What's next

With water already in the upper 40s to low 50s, expect the brown trout spawn to keep drawing fish into the shallower gravel runs over the next several days. Aggressive prespawn fish and egg-eating followers are the two bites to plan around. Sculpin-style streamers fished along the seam suit the first group, and Flylords Mag describes a sculpin ripped up a seam as the winning move on a recent 22-inch brown. Caddis Fly (OR) also points to jigged sculpin patterns and perdigons as fall standbys.

Flows look steady at the readings above, so we don't expect a sharp blowout in the short term. Fish the warmest part of the afternoon for the best chance at hatches, with Blue Winged Olives and midges typically the most dependable fall bugs. Tactical Bassin's fall coverage suggests that when baitfish are being chased, a swimbait with a blade adds flash and vibration, which can be worth a try on smallmouth bass in warmer, slower water.

The waxing gibbous moon puts bright light on the water into the evening, so low-light windows at dawn and dusk are still the safest bets for wary fish. Fishing the Midwest advises that October is prime time, with fewer boats out and fish feeding up as water cools, though that coverage is for other regions.

Context

Mid to late October is typically the heart of brown trout spawning season across much of the northern Rockies, so this timing is on schedule. Water in the upper 40s is normal for the period, and fish move from summer holding water toward spawning gravel and deeper winter lies. Anglers should check current Montana regulations, since some stretches carry seasonal closures or restrictions. MT FWP Fishing News also reports that the commission approved the 2027-28 fishing regulations this month, so rules for next season are changing. Some aquatic invasive species inspection stations remain open, and watercraft anglers should stop at any they pass.

Respecting redds matters most now. Wade carefully, avoid the clean gravel patches where fish have been digging, and handle spawners gently and briefly. Egg patterns and streamers draw the most attention, while small nymphs and midges keep working in the slower runs once the spawn tapers off.