Upper river: Drummond and Bearmouth to Milltown
The Clark Fork begins near Warm Springs and Anaconda as a small, meandering stream with a long history of mining pollution, and it stays a modest river through Deer Lodge and Drummond. Below Bearmouth Canyon, where I-90 access sites start, the trout numbers are still low until Rock Creek joins at Beavertail; from there to the Blackfoot confluence at Milltown it becomes a swift, braided river that guides mostly float from the Turah access. This is where the Clark Fork's one real salmonfly hatch happens in June.
The town stretch: Milltown to Kelly Island
The gauge on this page, Clark Fork above Missoula, sits at the top of the town water. Through Missoula the river is reached from Caras Park and the riverfront trails on both banks, and it fishes well by boat or on foot with dry-dropper, streamer and nymph rigs. The Bitterroot joins at Kelly Island on the west side of town, a large public area of braided channels.
Lower river: Kelly Island to Alberton Gorge and Superior
Below the Bitterroot the Clark Fork widens into long flats and slow runs that are float water more than wade water, an easy stretch that local shops recommend to new oarsmen. The Alberton Gorge is whitewater with good pocket fishing for those who can run it; below the gorge the Forest Grove and Dry Creek launches near Superior give long, mellow floats with deep pools and dry-fly flats down to Cascade Rapid.
Rainbow and brown trout
Rainbows and browns share the river below Rock Creek, with browns most prominent in the upper meadows and the biggest fish of either species in the lower river. The Clark Fork is known for its spring skwala stoneflies and Mother's Day caddis, its June golden stones and green drakes, and the August trico spinner falls that are the main event of late summer. Hoppers and fall baetis carry September and October.
Westslope cutthroat and northern pike
Native westslope cutthroat are present throughout and are catch-and-release; they benefited from the 2008 removal of Milltown Dam, which reconnected the Blackfoot and upper Clark Fork. Northern pike are established in the slow lower river and the sloughs and have no limit.
Season and regulations
From Perkins Lane bridge near Warm Springs down to the Flathead River the general season is the third Saturday in May through November 30, with a combined trout limit of 3, only 1 over 14 inches, and cutthroat catch-and-release. The extended season from December 1 to the third Saturday in May is catch-and-release for trout with artificial lures or maggots only. Artificial lures only within 100 yards of the mouths of Rattlesnake, Petty, Fish, Cedar, Dry and Trout Creeks and the St. Regis River. Above Perkins Lane the river is open all year, catch-and-release, artificial lures only, no fishing from boats.
Runoff peaks in late May and June and puts the river at many times its late-summer flow. Local guidance puts comfortable wading on the town stretch at roughly 500 to 1,500 cfs, with wading difficult above 3,000 cfs while floats remain good. Hoot-owl restrictions are common on the lower river in hot summers. The Montana FWP regulations and the restrictions page are the places to confirm all of this before a trip.