Fly fishing report · Midwest

Au Sable River

An Au Sable River report for Michigan trout water, RiverReports flow context, dry-fly hatches, streamer tactics, access, rules, and weather.

Check flow & weather

Today's river scoreHigh source confidence

Poor

Best option: Float.

A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

Updated Jul 13, 11:17 PM UTCUsually refreshes about every 45 minutes

Recommended approachFloat

Mode scores adjust the river-wide score for the risks of wading, bank fishing, or floating.

WadeCheck

Wading is the most sensitive plan today. Use protected edges only, avoid crossings, and downgrade quickly if clarity or current feels wrong.

Bank / edgeCheck

This report does not describe this as a primary mode. Verify legal access, depth, launches, and retreat options before planning around it.

Float · Best fit24/100

A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

Confirm before you leave

Flow and weather right now.

Use the flow trend to confirm the score before you leave. Weather can change the safest and most productive fishing window.

River strategy

Match the reach to the hatch and the rule.

The Au Sable is a famous Michigan trout river, but it is not one uniform report. Pick the branch or main-stem reach, confirm the trout rule, and use the flow trend before planning dries, streamers, or night fishing.

Use RiverReports and USGS Red Oak flow as broad main-branch context.
Check Michigan's Inland Trout and Salmon map before fishing a special reach.
Spring mayflies, June drakes, summer terrestrials, and fall streamers all have different setups.
Night fishing can be productive, but only with safe wading, legal access, and a clear exit plan.

Why this score moved

FlowLowers score

USGS shows 990 cfs with a stable over about 6 hours trend. same-date USGS history (1909-2025, 36 readings) puts normal around 684 cfs and the high-water marker near 784 cfs; today's flow is above that high-water marker. Treat this as high-water fishing: wading, clarity, crossings, and boat control need a conservative check.

Best mode nowLowers score

Float: A float can fit better than wading only if launches, shuttle, boat skill, wind, and local rules all check out.

Target choiceUse caution

Coldwater targets are a poor choice in this heat window, but warmwater targets may still be reasonable where legal and ethical.

Water temperatureUse caution

USGS water temperature is about 73F. Do not pressure trout or salmonids in warm water.

Public alertUse caution

A heat alert is active near this forecast point, so the score is capped until water temperature and fish-handling risk are checked. NWS alert: Heat Advisory issued July 13 at 3:38PM EDT until July 14 at 8:00PM EDT by NWS Gaylord MI.

Read the water

What changes the plan.

The Au Sable can be excellent when flows are stable and water stays cold. If it is hot, bright, or crowded, fish early, late, or choose shaded water with trout-safe temperatures.

Stable trout flow

Fish dries, soft hackles, and nymphs through riffles, flats, and bank edges.

Low clear water

Use long leaders, softer casts, and low-light windows.

Stained or rising

Streamers and bank work can improve, but skip unsafe wading.

Warm spell

Carry a thermometer and stop targeting trout when water is too warm for safe release.

Field plan

Fish it with intention.

Best flows

Use the RiverReports Main Branch chart and USGS 04136000 near Red Oak together. Stable flows support dry-fly and wade planning; sudden rain bumps, warm water, or poor clarity should shift the plan toward safer banks, colder windows, or a different reach.

When to skip

Skip or change reaches when Michigan trout-map rules are unclear, when warm water would stress trout, when night-fishing safety is poor, when access sites are too crowded for good etiquette, or when high water makes wading or boat control unsafe.

Local plan

Start by choosing the style: Grayling and Holy Water dry-fly focus, Mio and main-branch float context, Red Oak flow checks, or a streamer day after rain. Match flies and timing to that reach instead of treating the Au Sable as one generic river.

Backup water

If the Au Sable is warm, crowded, rule-sensitive, or off-color, compare the Boardman River, Pere Marquette River, or Little Manistee River after checking current rules, flows, and access.

Hatches & flies

Bring a flexible box.

TimingWhat to watchUseful flies

April to MayBlack stones, Hendricksons, BWOs, early caddisBlack stonefly nymph, Hendrickson, BWO emerger, caddis pupa

Reviewed family · report says “Black stonefly nymph”Black Stonefly PatternsBlack stonefly wording is a color and insect-group label, not one exact recipe. Size, nymph versus adult stage, wing profile, and weighting must remain explicit.See family guide

Reviewed family · report says “Hendrickson”Hendrickson PatternsHendrickson is a hatch name. Nymphs and emergers, upright or low-riding duns, and rusty spent spinners are different fly jobs.See family guide + 2 more reviewed guides in the Fly Box

Late May to JuneSulphurs, March Browns, Brown Drakes, caddisSulphur comparadun, March Brown, Brown Drake spinner, elk hair caddis

Reviewed pattern · report says “Sulphur comparadun”Sulphur ComparadunThe fan-shaped upright deer-hair wing, split tail, low hackleless body, and Sulphur-specific color define this destination. A PMD Comparadun is related but not interchangeable by name.See photos & how to fish it

Reviewed family · report says “March Brown”March Brown Dry FliesThis family includes traditional hackled, parachute, and Comparadun-style March Brown dries. Each exact construction rides differently and should be named when known.See family guide + 2 more reviewed guides in the Fly Box

June to AugustIsonychia, caddis, terrestrials, night brownsIsonychia, Stimulator, foam ant, beetle, mouse, small streamer

Reviewed family · report says “Isonychia”Isonychia and Mahogany Dun PatternsIsonychia nymphs are active swimmers; emergers, parachute or other dry forms, and spinners occupy different levels. Mahogany Dun can be regional hatch wording, so it does not identify one exact fly recipe.See family guide

Reviewed pattern · report says “Stimulator”StimulatorLook for a hair tail, dubbed abdomen with palmered hackle, tented hair wing, contrasting front hackle, and bright thorax or head. Colors and sizes vary widely and must remain labeled.See photos & how to fish it + 4 more reviewed guides in the Fly Box

September to NovemberBWOs, October caddis, salmon and steelhead movementBWO dry, October caddis, stonefly nymph, egg only where legal, leech

Reviewed family · report says “BWO dry”Blue-Winged Olive PatternsBWO describes a hatch group, not one fly. Nymph, emerger, dry, cripple, and spinner profiles must stay separate because they occupy different parts of the water column.See family guide

Reviewed family · report says “October caddis”October Caddis PatternsOctober Caddis names a hatch group. Amber or orange pupae, soft-hackle or wet forms, and large tent-wing adults fish at different levels.See family guide + 3 more reviewed guides in the Fly Box

Choose a specific reach before choosing a fly; the Au Sable changes quickly by branch and public access point.

In hatch windows, watch for spinner falls and bank feeders before blind casting.

Fish streamers near wood, undercut banks, and stained edges after rain or in fall.

For night fishing, scout the exit in daylight and keep wading simple.

During summer, take water temperature seriously and move to bass water if trout are stressed.

Access & responsibility

Know the entry. Know the exit.

Michigan DNR's current fishing regulations and Inland Trout and Salmon map control seasons, methods, size limits, and reach boundaries. Verify the specific Au Sable reach before fishing.

Grayling and Holy Water context

Classic upper/mainstream fly-fishing planning with exact rules to verify.

Mio and Red Oak main branch

Useful main-stem flow context and broader boat/wade planning.

Huron-Manistee public access sites

Use official access and boat-launch information rather than informal bank cuts.

Transparent sources

Check the facts behind the plan.

Last material review: 2026-05-31

flowRiverReports Au Sable Main Branch near Parmalee flowUSGS Au Sable River near Red Oak 04136000 regulationMichigan fishing regulations accessMichigan Trout Trails backgroundMichigan Natural Rivers program backgroundRivers.gov Au Sable River safetyNational Weather Service point forecast

Common questions

Before you leave.

What should I check first before fishing the Au Sable River?+

Check the Red Oak flow, Michigan trout map, weather, and water temperature before picking a reach.

Are there special regulations on the Au Sable River?+

Yes. The system has reach-specific trout rules, so check the Michigan Inland Trout and Salmon map directly.

Is the Au Sable River a good fly-fishing river?+

Yes, but only if you match the reach, season, water temperature, and target species. This page separates trout, migratory, and warmwater plans where that matters.

What flies should I bring for the Au Sable River?+

Bring the hatch-chart flies, a few confidence nymphs, and a backup streamer or warmwater box so you can adjust to flow, clarity, and temperature.

How should I plan access for the Au Sable River?+

Access is good in many places, but private banks, boats, and special reaches make planning important.