Henry's Fork
HENRY'S FORK
ReportOvercast 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 | Overcast midday |
| Mahogany Dun | #16–18 | Moderate, weather-dependent | Overcast midday |
| October Caddis | #10–12 | Active adults | Late afternoon |
- OVERCAST MIDDAY (11 AM–2 PM): Prime window for pseudo BWO and mahogany dun dry fly action; look for dense hatches when clouds hold.
- LATE AFTERNOON (3–6 PM): October caddis adults become active; swing or dead-drift a #12 caddis dry along the banks.
- EARLY MORNING / LOW LIGHT: Best time for streamers targeting migrating brown trout below Ashton Dam and around St. Anthony.
