Quick reference

Field Value
State / region Michigan, Northern Lower Peninsula (Grayling to Oscoda)
Species Brown trout, brook trout, rainbow trout; steelhead and salmon in the lower river
Best months May–September for resident trout; late June for the Hex hatch; March–May and October–November for steelhead
Water type Freestone with strong spring influence; tailwater-like below Foote Dam
Difficulty Intermediate — forgiving wading and dense wild fish, but pressured trout and night-time Hex fishing raise the bar
Wading Generally very good at normal flows in the upper river; the Trophy Water and lower river demand caution or a boat at higher flows

Why fish here

The Au Sable is the reference point for Midwestern trout fishing. It flows roughly 138 miles west to east across Michigan's northern Lower Peninsula before entering Lake Huron at Oscoda, and along the way it packs in an unusual range of fisheries: dense wild brown and brook trout in the medium-gradient freestone water around Grayling, trophy brown trout streamer water below Mio, and steelhead and salmon runs below Foote Dam. Few single watersheds give a fly angler this much variety without leaving the river.

The core draw is wild trout density and consistent dry-fly fishing from late April through October. The famous nine-mile "Holy Waters" reach near Grayling is managed fly-fishing-only and catch-and-release, and it fishes like it: educated, abundant wild browns and brookies rising to a long procession of mayflies and caddis. Then there is the Hexagenia hatch. From mid-June through early July — peaking around the last week of June — the giant Hex mayflies come off after dark, and the river's largest browns feed on the surface at night. It is the event of the season and a primary draw for experienced night anglers.

Downstream, the character changes twice. The Trophy Water from Mio supports year-round streamer fishing for large browns in bigger, more powerful water. And below Foote Dam, spring and fall steelhead plus fall Chinook, coho, and Atlantic salmon turn the lower river into a migratory fishery. One watershed, three distinct trips.

The river, section by section

Holy Waters (Burton's Landing to Wakeley Bridge)

Access: Burton's Landing at the upper end, Wakeley Bridge at the lower end, plus roadside pull-offs along the county roads near Grayling; both endpoints are established, well-documented access sites for this nine-mile reach. Character: Medium-sized freestone with moderate gradient, classic riffle-run-pool structure, and abundant woody cover. Knee-deep riffles to waist-deep runs and pools; wading is very good at normal flows, with roughly 150–350 cfs at the Grayling gauge often cited as ideal. Species mix: Primarily wild brown trout with a strong brook trout presence — managed for quality wild fish, not stockers. Crowding: One of Michigan's most popular fly-fishing reaches. Busy on spring and early-summer weekends and packed during prime hatches and Hex season; weekdays and shoulder seasons run much lighter. Notable hatches: Hendricksons and early mayflies late April–May, Sulphurs and assorted summer mayflies, strong caddis all summer, and the Hex hatch mid-June through early July.

This is the water that made the river's name, and the regulations keep it honest: fly-fishing only, catch-and-release, open year-round under special rules. The structure rewards methodical fishing — working woody cover and pool tails with accurate drifts rather than covering miles. During Hex season the reach fishes at night, with anglers staking out pools before dark and listening for the heavy rises of big browns on size 6–8 duns and spinners.

Mainstem Trout Water (Grayling area outside the Holy Waters)

Access: Various public access around Grayling — city launches, bridges, roadside pull-offs — plus additional state- and locally-managed sites upstream and downstream. Grayling is the hub. Character: Similar freestone character with more variety: tighter bends, undercut banks, mixed shallow runs and deeper pools. Wading is the standard approach and generally safe at typical flows; canoes and drift boats are common at higher water and for covering distance. Species mix: Wild browns dominate, brook trout hold in cooler, spring-influenced water upstream, and a few smallmouth bass appear in warm-season lower-gradient reaches. Crowding: Moderate to heavy in spring and early summer near easy access; drops at midday in midsummer and thins to dedicated anglers in late fall and winter. Notable hatches: The full northern Michigan slate — early brown stoneflies in late winter and spring, Hendricksons in April–May, Sulphurs and Light Cahills into early summer, multiple caddis species all summer, midges and small mayflies in cold-water periods, and Hex in the slower backwater reaches from mid-June into early July.

The Grayling-area mainstem is where anglers escape the Holy Waters crowds without giving up much fishing. The undercut banks and bend pools hold fish that see slightly fewer flies, and the mix of wadeable riffle water and floatable distance suits both approaches. It is also the natural base for a first Au Sable trip: lodging, access, and varied water all within minutes of town.

Trophy Water (Mio Dam to McKinley / Alcona)

Access: Mio Dam access, Comins-area access, McKinley Trail Access, Red Oak-area access, and other established public sites along the reach, which guide literature describes as Mio to McKinley or Mio to Alcona Dam Pond. Character: A larger, more powerful mainstem — deeper runs, long pools, stronger current, with reservoir influence from Mio and Alcona ponds. Wadeable in many spots at moderate flows, but flows up to about 1,300 cfs are the usual wading ceiling; at 1,400–1,600 cfs use extreme caution or a boat. Drift boats and river sleds are the standard tools for swinging streamers along the structure-rich banks. Species mix: Managed as Trophy Water primarily for large brown trout, with year-round streamer fishing for trophy fish between Comins and McKinley. Brook trout are scarce in this bigger water; migratory fish enter well downstream. Crowding: Pressure concentrates in windows — streamer anglers fall through early spring, Hex and big-dry anglers on early-summer nights. Prime-period weekends see real guide and private-boat traffic; weekdays and non-hatch nights are quiet. Notable hatches: The same broad mayfly and caddis slate as upstream, headlined by the Hex hatch and its night fishing for very large browns mid-June to early July; stoneflies, Sulphurs, Cahills, and caddis through spring and summer, midges and Baetis in cold months.

This is where the river's biggest resident browns live, and the fishing reflects it: fewer, larger fish, moved by big streamers on sink-tips or by size 6 Hex patterns in the dark. The year-round special regulations protect the large fish that make the reach worth the effort. Check the Mio gauge before planning to wade — the difference between 1,200 and 1,500 cfs is the difference between a wading trip and a boat trip.

Lower Au Sable (Foote Dam to Lake Huron)

Access: Foote Dam access area, Foote Dam Pond, and multiple public sites and boat ramps downstream toward Oscoda. Character: Below Foote Dam the river becomes a larger, tailwater-like flow with deeper runs and pronounced holding water for migratory fish. Wading works in select riffles and near shore, but much of the fishing happens from bank positions or boats with heavier tackle and sink-tips. Current is strong; clarity varies with runoff. Species mix: Spring steelhead March–May (peak often April), fall steelhead October–November, and fall Chinook, coho, and Atlantic salmon September through November. Resident trout are present but not the point. Crowding: Significant during peak runs, especially fall weekends in good water. Weekdays and off-peak flows are manageable; winter is quiet apart from locals. Notable hatches: Hatches matter less here. Egg patterns, nymphs, and streamers take most migratory fish; the resident insects are background noise.

The lower river is a different sport wearing the same river's name. Plan it around run timing rather than hatch charts: April for peak spring steelhead, October–November for fall fish and salmon. An April trip can realistically pair morning steelhead below Foote Dam with afternoon trout water near Grayling — one of the stronger two-fisheries days available in the Midwest.

Hatches and seasons

Months Hatches Flies
Mar–Apr Early brown stoneflies, midges, early Baetis/BWOs; Hendricksons on warm late-April days Early Brown Stone nymphs and dries #10–12, Zebra Midge #18–22, Parachute Adams #14–18, Hendrickson dry #12–14, Pheasant Tail #14–18
May Medium brown stoneflies, Hendricksons, Sulphurs, mixed mayflies, building caddis including Little Black Caddis Parachute Sulphur #14–18, Light Cahill #12–16, Elk Hair Caddis #14–18, Hare's Ear #12–16, Yellow Sally patterns #12–16
Jun–early Jul Little Yellow Stones, Golden Stones, evening mayflies, strong caddis, and Hexagenia limbata at night mid-June–early July Hex dries and spinners #6–8, Yellow Stimulator #8–14, Chernobyl Ant #8–12, Parachute Adams #12–16, Elk Hair Caddis #12–16
Jul–Sep Summer mayflies (Cahills, small Sulphurs), caddis, terrestrials, sporadic evening spinner falls Yellow Humpy #10–18, Griffith's Gnat #18–22, Parachute Adams #14–18, Chernobyl Ant #8–12, Elk Hair Caddis #14–18
Oct–Feb Sparse surface activity; midges and small BWOs on mild days; nymphs and streamers carry the season Black Woolly Bugger #6–8, Zoo Cougar #4, Pheasant Tail #16–18, small BWO dries #18–22, Zebra Midge #20–22
Season Top patterns Why
Spring Parachute Adams #14–18, Hendrickson dry #12–14, Pheasant Tail and Hare's Ear #12–18, Early Brown Stone nymphs/dries #10–12, Woolly Bugger #6–8 Matches the early stoneflies, Hendricksons, and mixed mayflies behind the river's celebrated spring dry-fly fishing, with subsurface options for cold or high water
Summer Hex patterns #6–8 at night, Yellow Stimulator #8–14, Elk Hair Caddis #12–16, Parachute Sulphur #14–18, Chernobyl Ant and terrestrials #8–12 The mid-June to early-July Hex hatch produces the biggest browns of the year; smaller mayflies, caddis, and terrestrials cover daytime and evening fishing all summer
Fall Woolly Bugger and baitfish streamers #4–8, Zoo Cougar #4, egg patterns #8–12, stonefly nymphs #8–12, small mayfly nymphs #14–18 Streamer fishing for trophy browns is excellent October through early May in the Trophy Water; eggs and stonefly nymphs handle fall steelhead and salmon below Foote Dam
Winter Black Woolly Bugger #6–8, Pheasant Tail #16–18, Zebra Midge #20–22, small BWO dries #18–22 on mild days Cold-water trout feed on small nymphs and midges in deeper runs; slow-stripped black streamers and compact nymph rigs are the recommended winter program

Gear notes

A 9-foot 5-weight with a weight-forward floating line is the standard Au Sable tool and covers roughly 80 percent of situations — all the dry-fly and light nymph work in the Holy Waters and Grayling reaches. Step to a 6-weight for larger streamers and Trophy Water browns, and bring a 7–8-weight for steelhead and salmon below Foote Dam. Leaders run 9 feet tapered to 3X–5X for trout, 0X–2X for big streamers, and 6–8 lb tippet on steelhead rigs. Chest or waist-high waders with felt or well-lugged rubber soles handle the mostly wade-based fishing; treat the higher-flow Trophy Water with respect.

Logistics

  • Regulations: Managed by the Michigan Department of Natural Resources (MDNR), and section-specific to a degree that demands reading the current guide. The Holy Waters (Burton's Landing to Wakeley Bridge) is fly-fishing-only, catch-and-release, open year-round under special rules. The South Branch (Chase Bridge to mouth) and North Branch (Sheep Ranch to mouth) contain flies-only and catch-and-release sections, and the Trophy Water from Mio to McKinley/Alcona carries year-round special regulations protecting large browns. Flies-and-lures-only areas, varying size and bag limits, and gear rules apply elsewhere. Anglers 17 and older need a Michigan all-species license plus the trout endorsement for designated trout waters. Regulations change annually — verify current MDNR rules before fishing.
  • Access points:
    • Burton's Landing — upper end of the Holy Waters; wade and boat access
    • Wakeley Bridge — downstream end of the Holy Waters; parking and entry to the fly-only reach
    • McKinley Trail Access — Trophy Water reach below Mio; a noted streamer area for large browns
    • Foote Dam — the major steelhead and salmon access on the lower river; shoreline and boat access below the dam
  • Closest fly shop: Streamside Au Sable River Fly Fishing Guides — Gates Lodge/Grayling area
  • Nearest towns: Grayling, Mio, Oscoda, Comins
  • Closest gauge: USGS 04136500 — Au Sable River at Mio, MI. For the middle and Trophy Water reaches, wading is generally acceptable up to about 1,300 cfs; treat 1,400–1,600 cfs as extreme-caution territory and prefer a boat above that.

When NOT to fish here

Stay off the Trophy Water when flows approach or exceed 1,400–1,600 cfs — wading turns hazardous and clarity often fails. In midsummer heat waves, shallower reaches can push near or past safe trout temperatures; ethical practice limits fishing to cool mornings, evenings, or spring-influenced sections until temperatures drop. And know what crowds you are walking into: peak Hex nights in late June and prime steelhead and salmon weekends below Foote Dam are the river's busiest moments. Anglers who want the river to themselves should target shoulder periods and the less famous hatches instead.

Where to fish next

  • Fly Fishing in Michigan — the full state guide
  • Manistee River — the Au Sable's west-flowing counterpart, with its own flies-only water from M-72 to CCC Bridge
  • South Branch Au Sable River — the flies-only Chase Bridge-to-mouth section offers quieter wild-trout water in the same system