Henry's Fork
HENRY'S FORK
ReportHenry's Fork, October 28th, 2026. Overcast conditions and right after storms offer the best dry fly fishing, which is slowly diminishing in quality. The river is low, cold, and clear throughout. Low flow out of Island Park Dam makes wading easy from Box Canyon through the Harriman reach. Fish are concentrated in deeper water.
Nymphing remains the best producer in Box Canyon, where low flow is rough on hard-sided boats. Weather is reducing terrestrial insect numbers significantly. Tiny BWOs (pseudos) emerge best during overcast middays when dense hatches can occur. Same for mahogany duns. October caddis are active during late afternoons.
Brown trout are migrating upstream and are the big attraction to fishing in the river above and below Ashton Dam and around St. Anthony. Streamer patterns during low light and stormy conditions and early mornings are the best producers. Flow at Box Canyon is about 90 cfs, below Ashton Dam is about 700 cfs, and about 1,100 cfs at St. Anthony.
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Blue-Winged Olive (Pseudos) | #22–24 | Dense hatches possible; best on overcast days | Midday (overcast) |
| Mahogany Dun | #16–18 | Active; best under cloud cover | Midday (overcast) |
| October Caddis | #8–10 | Active adults on the water | Late afternoon |
| Baetis Nymphs (subsurface) | #20–22 | Consistent subsurface; nymphing best producer in Box Canyon | All day |
- MIDDAY (overcast only): Fish BWO and mahogany dun dries during dense pseudo hatches on the Harriman reach and Box Canyon
- LATE AFTERNOON: Switch to October caddis dries as adults become active along the river
- EARLY MORNING / LOW LIGHT / STORMY: Strip streamers for migrating brown trout above and below Ashton Dam and around St. Anthony
