September's hatch rows look thin next to June's, and that is the point of the month. On this site's charts, Tricos are still at peak on only five rivers in September, hoppers on five, Blue-Winged Olives are on almost everywhere but not yet at peak, and a handful of insects nobody thinks about the rest of the year, crane flies and October Caddis, show up in the columns. The fishing is a transition, and the rivers that fish best are the ones where two of those rows overlap.
Blue-Winged Olives coming back on
The fall Baetis brood is the month's big story, but September is its beginning rather than its peak. On nearly every river charted here the BWO row reads on in September and peak in October; the only river with BWO at peak in September is the Firehole, whose thermal water runs on its own calendar. In practice that means the first gray, drizzly afternoon of September brings the first real Baetis emergence on the Missouri, Bighorn, Madison, Middle Provo, Frying Pan, and San Juan, and a warm sunny one brings almost nothing. Size 18 to 20 to start; they get smaller as fall goes on. See the BWO guide.
Where hoppers are still at peak
Terrestrials fade with the first hard frost, but the charts keep grasshoppers at peak in September on five rivers: the Bitterroot, Yellowstone, New Fork, Snake in Wyoming, and the South Fork of the Snake. The Green below Flaming Gorge shows its general terrestrials row at peak in September as well. On the rest of the Montana and Idaho freestones, the Madison, Big Hole, Blackfoot, Gallatin, Clark Fork, Salmon, and Lochsa, hoppers read on: still worth throwing on a warm afternoon, no longer the whole game. Go a size smaller than August, 10 to 14, in tan and rust to match the late-season naturals, and fish ants and beetles on the cool days.
The last of the Tricos
Trico spinner falls run into September on the rich, slow water and end there. The five rivers with Tricos at peak in September are the Missouri, Bighorn, Madison, Henry's Fork, and Silver Creek. The Colorado tailwaters (Frying Pan, Blue, Taylor, Gunnison, South Platte, Arkansas), both Provos, the Boise, Teton, Hat Creek, Owens, and San Juan read on. As mornings get colder the spinner fall shifts later, from sunrise toward mid-morning, and gets shorter. Size 22 to 24 spinners, 6X or 7X.
Crane flies and the September caddis
Two rows peak in September that do not peak in any other month. Crane flies are marked at peak in September on eight rivers, seven of them in Utah: the Provo, Middle Provo, Weber, Ogden, Logan, Blacksmith Fork, and Strawberry, plus the Madison. The larva is the fly that matters: a size 8 to 12 tan or olive crane fly larva, dead-drifted deep through the riffles. The adults skate on the surface in the afternoon, and a size 12 skated crane fly will move fish on the Logan and Blacksmith Fork.
Caddis hit peak in September on the Deschutes, Klickitat, Lochsa, St. Joe, South Fork of the Flathead, and both Snakes. And the October Caddis (Dicosmoecus), the big orange one, comes on in September ahead of its October peak on the Deschutes, Metolius, North Umpqua, Rogue, Clearwater, Klickitat, Methow, and Yakima. A size 8 to 10 orange Stimulator skated at dusk, or the cased larva fished deep in the morning.
Browns beginning to stage
Brown trout spawn in the fall, and September is when the biggest ones start to move: upstream toward tributary mouths and gravel tailouts, out of the deep summer lies and into water where you can reach them. They are not on redds yet, and they are not done eating. This is the month streamers start to outfish nymphs on brown-trout water like the Weber, Middle Provo, Madison, Big Hole, Missouri, Taylor, and East Walker. The full behavior picture, and how to fish around spawning fish without fishing to them, is on the fall trout behavior page.
Steelhead rivers where September is the start
On the anadromous rivers the month means something different. The Clearwater and Salmon in Idaho are steelhead water, and the Klickitat, North Umpqua, and Rogue are summer-steelhead rivers where September fishing overlaps with the October Caddis. Seasons and gear rules on those rivers are set by the state agencies and change; check them before you plan around a run.
The September box
- Hoppers 10 to 14, ants 16 to 18, for the warm afternoons.
- Trico spinners 22 to 24, if you are on one of the five peak rivers.
- BWO nymphs and emergers 18 to 20, for the first gray afternoon.
- Crane fly larva 8 to 12 on the Utah rivers and the Madison.
- Orange Stimulators 8 to 10 for the October Caddis rivers.
- Two or three streamers, olive and black, and a sink tip, for the browns.