The forks and Darby
The Bitterroot proper starts where the East and West Forks meet just south of Darby and flows north, so downstream is north toward Missoula. The West Fork below Painted Rocks Dam gives cold releases through summer; the East Fork is smaller freestone water. The Darby gauge on this page sits at the top of the main stem near Hannon Memorial access, and the upper river from here to Hamilton is quick, riffly water that guides call a cutthroat stronghold, fished from the bank early and late in the season and by boat when flows allow.
Hamilton to Stevensville
The middle river braids into side channels and log jams between Hamilton, Victor and Stevensville, with FWP access sites off US 93 and the Eastside Highway. Rainbows, browns and cutthroat all live here. Wading is possible at the access sites but the channel changes every runoff, so local shops are the best source on which channels carry water in a given year.
Stevensville to Missoula
Below the Stevensville bridge the river widens into long runs and deep pools, the fish-per-mile count drops and the average size rises. This is the brown trout and big rainbow water, the least wade-friendly stretch, and it ends where the Bitterroot joins the Clark Fork at Kelly Island on the west side of Missoula. Northern pike are present in the lower river, and any smallmouth bass caught below Florence Bridge must be killed and reported to FWP.
Westslope cutthroat
Native westslope cutthroat dominate the upper river south of Hamilton and are common the whole way down. They are catch-and-release throughout the Bitterroot and its forks and are the fish that make the spring skwala fishing and the summer attractor fishing what they are.
Rainbow and brown trout
Rainbows are spread through the system and browns are most numerous in the lower river, where they grow largest. Skwala stoneflies in March and April bring the biggest browns of the year to the surface; salmonflies start on the East and West Forks in early June and reach the main stem later in the month; the fall brings mahogany duns, then streamer fishing for pre-spawn browns.
Season and regulations
The general season runs from the third Saturday in May through November 30, and the extended season from December 1 to the third Saturday in May is catch-and-release for trout with artificial lures only. Cutthroat are catch-and-release everywhere. From the forks to Woodside Bridge and again from Florence Bridge to the mouth the combined limit is 3 rainbow or brown trout with only 1 over 14 inches; from Woodside Bridge to Florence Bridge all trout are catch-and-release and artificial lures only. Commercial and nonresident floating is restricted by day of the week on the West Fork and upper river from June 1 to September 15.
Runoff peaks in May and June and can pass 10,000 cfs at Darby. Local reports put comfortable wading on the upper river at roughly 200 to 800 cfs, with wading getting difficult above 1,200 cfs; floats work at higher flows. Summer hoot-owl restrictions are common on the lower river in hot years. Check the current Montana FWP regulations before you go.