Michigan Trout Hatch Calendar
Month-by-month emergence timing for the AuSable, Manistee, Pere Marquette, and Michigan's other classic trout rivers.
Knowing when each hatch is on is the difference between a good day and a great one on Michigan's trout streams. Chris Izworski lays out the master calendar of mayfly, caddis, and stonefly emergence across the AuSable, Manistee, Pere Marquette, and the rest of the Mitten.
Early-season hatches
Michigan trout season opens in late April on most designated trout water. Water temperatures sit in the high thirties to low forties, which means surface activity is limited but real. The first major mayfly hatch is the early black stonefly (Capnia), tiny size 16-18 dark stoneflies that crawl out of the water column onto banks and rocks. Trout key on the nymph stage more than the adult. Black stonefly nymphs and small dark olive baetis (BWO) nymphs are the dominant subsurface food.
By late April, the first hendricksons (Ephemerella subvaria) appear on the AuSable mainstem, the Pere Marquette, and the lower Manistee. Hendricksons are the signature April-into-May hatch in Michigan and the first mayfly emergence that drives consistent surface feeding. Hatches typically run from about 2:00 PM to 4:00 PM in cool weather, shifting earlier as water warms. The Hendrickson hatch is covered in detail on the dedicated page.
The heart of the season
May is the busiest hatch month in Michigan. Hendricksons continue through the first two weeks, overlapping with mahogany duns and the first caddis emergences. The Mother's Day caddis hatch (Brachycentrus americanus and other grannom species) is a significant event on the AuSable, the Pere Marquette, and the Boardman, typically peaking in the second week of May. By mid-May, sulphurs (Ephemerella dorothea, Ephemerella inermis) start emerging in late afternoon and continue well into June.
March browns (Maccaffertium vicarium) emerge sporadically through May on most Michigan rivers, providing an early-evening hatch when conditions are right. Large dark stoneflies (Pteronarcys dorsata, the giant stonefly) are also active in May on the AuSable and the lower Manistee, although the hatch is less reliable than mayfly emergences. The Hendrickson, sulphur, BWO, and caddis hatch pages cover the specifics of timing and fly selection for each.
The famous Michigan hatch
June is hex month. The hexagenia limbata hatch (Michigan mayfly, big yellow mayfly, fishfly) emerges from silt-bottomed slow-water sections of the AuSable, the Manistee, the Muskegon, and several other rivers in the last two weeks of June and the first week of July. Adult hexes are size 4 to 6, cream-yellow, and emerge after dark in a brief window roughly 9:30 to 11:30 PM. Big browns that have not eaten in daylight all year feed aggressively on hexes. The AuSable hex hatch is a destination event with a full dedicated tracker page.
Earlier in June, sulphurs finish their run, brown drakes (Ephemera simulans) emerge in the same silt-bottomed slow water that produces hexes, and isonychia (slate drake) start their summer-long emergence. June is also the start of the gray drake (Siphlonurus) hatch on the AuSable mainstem and the Manistee. Caddis emerge throughout the month with multiple species overlapping. The trout are eating well, and there are usually three or four hatches active on any given day.
Summer terrestrial and trico season
Once the hex hatch ends in early July, the dominant insect activity shifts to terrestrials (grasshoppers, beetles, ants, cicadas) falling from bankside vegetation, plus trico (Tricorythodes) spinner falls at dawn and isonychia emergences in the late afternoon and evening. Trout move into shaded bank water and feed selectively on hopper-dropper rigs through the heat of the day. Surface activity tapers in midday but returns in the cooler hours.
August adds terrestrial cicadas in some years (periodical cicada cycles) and continued isonychia activity. Trico spinner falls produce excellent dry-fly fishing in the first two hours of daylight if you are willing to be on the water by 6:00 AM. The white fly hatch (Ephoron leukon) appears on the lower Manistee, the Muskegon, and a few other rivers in late August, producing an evening spinner fall worth chasing. By late August, water temperatures on the warmer downstream sections of the Manistee and Muskegon push 70 degrees and trout fishing should pause until the river cools.
Fall hatches and pre-spawn behavior
September brings cooler nights, dropping water temperatures, and a return of mayfly emergence. The fall baetis (BWO) hatch picks up in the second half of September and runs into October on most Michigan trout rivers. Hatches happen midday during overcast or rainy weather. Late October adds October caddis (Dicosmoecus) on a few rivers and the start of the brown trout spawn, after which serious anglers leave wild browns alone and target other species.
Streamer fishing peaks in October as pre-spawn browns move and feed aggressively. Steelhead enter the lower Pere Marquette, the Muskegon, and the Manistee from Lake Michigan beginning in late October, providing a separate fishery into the winter. November and the off-season are covered in the streamer fishing and winter trout sections.