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.
Try terrestrial patterns during warm mid-days and use long, drag-free floats on fine leaders with precise casting toward banks. Tiny BWOs (pseudos) emerge best during overcast mid-days 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 for fishing in the river above and below Ashton Dam and around St. Anthony. Streamer patterns during low-light conditions and early mornings are the best producers. Flow at Box Canyon is about 90 cfs, below Ashton Dam is about 600 cfs, and about 850 cfs at St. Anthony.
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Blue-Winged Olive / Pseudo (Baetis) | #22–24 | Moderate — best on overcast days | Mid-day (overcast conditions) |
| Mahogany Dun | #16–18 | Moderate — overcast dependent | Mid-day (overcast conditions) |
| October Caddis | #8–10 | Active | Late afternoon |
| Terrestrials (ants, hoppers) | #12–16 | Productive during warm spells | Warm mid-day |
| General Nymphs (subsurface) | #12–20 | Best overall producer | All day — especially Box Canyon |
- FIRST LIGHT TO EARLY MORNING: Swing and strip streamer patterns near Ashton Dam and St. Anthony for migrating brown trout
- WARM MID-DAY (11 AM – 2 PM): Fish terrestrial patterns (ants, hoppers) along grassy banks with long, drag-free drifts on fine tippet
- OVERCAST MID-DAY / LATE AFTERNOON: Watch for BWO and mahogany dun hatches under gray skies mid-day; switch to October caddis patterns as afternoon light fades
