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Emergence Triggers
Water Temp
40–54°F
Flow
Stable to gently dropping
Light
Overcast, drizzle — the nastier the better
Water Type
Riffles, tailouts, soft seams
Lifecycle
How Trout Eat It — Stage by Stage
1
Nymph
Year-round
Trout eat Baetis nymphs daily. Swimmer nymphs get active and drift hours before emergence — dead-drift deep in riffles.
Match It
Pheasant Tail#16-20
$2.75RS2#18-22
$2.95Juju Baetis#18-20
$3.252
Emerger
First 30 min of hatch
The highest-percentage stage. Fish key on cripples stuck in the film — look for subtle head-and-tail rises.
Match It
Barr's Emerger#18-20
$2.95Sparkle Dun#18-20
$3.153
Dun
Peak hatch, 1-3pm
Duns ride long on cold days. Classic dry-fly fishing to steady risers in slow seams.
Match It
Parachute BWO#18-20
$3.25Comparadun BWO#18
$3.154
Spinner
Evening, calm days
Rusty spinners collect in back-eddies at dusk. Sippers in flat water are usually on spinners, not duns.
Match It
Rusty Spinner#18-20
$2.95Cross-Reference
Where This Bug Matters
Gallatin River
Big Hole River
Madison River
Spring and fall staple
Missouri River
Yellowstone River
Fall afternoons below Livingston
Flathead River
Beaverhead River
Bighorn River
Colorado River
Best on snowy spring afternoons
Henrys Fork
Spring and fall — the Ranch closer
Deschutes River
Winter and spring afternoons
≋ Waterlands · Hatch data blends USGS gauges, NOAA temps & regional emergence records
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