Freestone · Sand Gravel · Michigan, US

Au Sable River

Aerial view of the Au Sable River winding through forested banks in autumn, Michigan

The Au Sable is two rivers in one: the upper 'Holy Water' is a hallowed resident brown-trout flies-only stretch, hatch-rich and technical, while the lower river below Foote Dam gets Lake Huron steelhead and a fall salmon run.

Today · Slow going — pick your moments
Blue Winged Olive
Forecast · Today
Slow going — pick your moments
Slow going — pick your moments and do not force it.
80% projected
Today's fly
Blue Winged Olive
Blue Winged Olive
Conditions on the water · Today
Live gauge
Level
Rising
1.02 m
Lifting fast
Water temp18.0°C
ClarityVery coloured
Weather24°C
WindN 15 km/h
Pressure1013 hPa
Rain · recent28.8 mm
Rain · ahead1.1 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Warm — slow
18°C est.ideal 1016°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Water at 19.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Hatch timeline · todayPeak at 12pm

12pm(now) Grasshopper (Eastern)

Stage: Terrestrials on topApproach: Dry flyActivity: 55%
Also:Reed Smut33%Trico (Eastern)26%
Peak emergence windowWeather boostEmergence building5 food groups active

Peak activity at 12pm — Grasshopper (Eastern) (Grasshopper (Eastern), Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Brown DunHatch
2
3
3
3
3
3
3
2
Quill GordonHatch
2
2
Blue QuillHatch
2
3
2
HendricksonHatch
2
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
Local fly shops: Gates Au Sable Lodge
Permits & access
Permit required — see local rules.
  • Michigan licence
  • The upper Holy Water is flies-only, no-kill — verify MI DNR rules by reach
  • Lower-river runs are an introduced, harvestable sport fishery.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 1
Water here at 19.2°C — the fishing's alive, but these are cooler if you'd rather rest the warm water.
Gallery · 2
  1. Aerial view of the Au Sable River winding through forested banks in autumn, Michigan
    The Au Sable River bends through autumn forest at High Banks Overlook, Michigan
  2. Terrain map of the venue
    Terrain map
About this water

The Au Sable is two rivers in one: the upper 'Holy Water' is a hallowed resident brown-trout flies-only stretch, hatch-rich and technical, while the lower river below Foote Dam gets Lake Huron steelhead and a fall salmon run. The birthplace of Trout Unlimited, and it fishes like a place that earned the name.

Under the surface

The Au Sable's Holy Water is exactly that to a Michigan trout angler — the special-regulation water below Grayling where Trout Unlimited was founded in 1959, on the banks of a river worth founding it for. It runs through the jack pine and cedar of northern Michigan as a clear, cold, spring-fed river of remarkable evenness — the sand-country geology gives it a steady flow and a steady temperature, and the wild browns and brook trout rise to its famous hatches with reassuring regularity. The bed is sand and gravel, the water tea-stained and gentle, the banks lined with cedar sweepers and the long-tailed Au Sable riverboat drifting through. The current is mild, the gradient soft. Wading is easy on firm gravel, with soft sandy pockets to mind. This is classic, civilized, deeply loved eastern trout water — the kind of river you measure other rivers against, and a few of them come up short.

Wading: Soft sandy pockets among the gravel

  • Sand gravel
  • Unconfined
  • Pool riffle
The full read · show the working · for Brown Trout · confidence 80%
How the 33 is built — score × weight = contribution
Temperature22 × 28%6.2
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time80 × 13%10.4
Pressure80 × 7%5.6
Insect activity63 × 12%7.6
Limiting factor: Water temperature (19.2°C) is outside Brown Trout's preferred range (10–16°C)= 65
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
Related guides
Booking & contacts