Au Sable River · hatch chart
The Hex hatch in the last week of June is the event; the trout season closes at the end of September
By month
JanFebMarAprMayJunJulAugSepOctNovDec
| Month | Insect | Stage | Size | Time | Intensity |
|---|---|---|---|---|---|
| Apr | Hendrickson (Ephemerella subvaria) | Dun | #12-14 | 13:00-16:00 | |
| May | Sulphur (Ephemerella invaria) | Dun and spinner | #14-16 | 19:00-21:00 | |
| Jun | Hexagenia limbata | Dun, after dark | #6-8 | 22:00-00:30 | |
| Jun | Brown Drake (Ephemera simulans) | Dun at dusk | #10-12 | 20:30-22:30 | |
| Jul | Trico (Tricorythodes) | Spinner fall | #22-24 | 08:00-10:30 | |
| Aug | Terrestrials — ants and hoppers | Adult | #12-16 | 10:00-17:00 | |
| Sep | Blue-Winged Olive (Baetis) | Dun | #18-20 | 13:00-16:00 |
Flow and visibility
Because the feeders are springs, the Au Sable stays cold and clear when other Michigan rivers are muddy in April. The dam at Mio smooths the lower river; above it, flows follow rainfall and the river can colour up for two days after a storm. By August the water is often too warm to fish ethically after noon, and the productive hours move to dawn and after dark.
The insect plate
