Au Sable River below Mio (Trophy Water to Alcona)

Michigan's biggest hatch and the last of the Au Sable's Big Five: 4-8 duns emerging in the dark from silt banks on muggy nights from about 10 pm, with spinner falls one to three nights after the first duns. Peak on the Au Sable Holy Water is June 20-28 (Mio Trophy Water is the classic Hex water), Manistee June 25-July 5, Pere Marquette June 10-25, Muskegon tailwater June 8-20, and the U.P. two to three weeks later (Superior Flies peak July 5-21). Fish a Hex dun or spinner such as Robert's Yellow Drake, McCoy's All Day Dun or a Boondoggle Hex on a short 6-foot 2X leader, and a Hex wiggle nymph or Spring Wiggler year-round; trout in prime habitat may see up to 2,000 nymphs a day outside the hatch. Watch water temperature from June 10 and expect the hatch within days once the Au Sable holds 62-65 F.

The third of the Au Sable's Big Five: short-lived, blizzard-like hatches from about 8 pm to midnight in the first half of June on the northern rivers, late May on the Pere Marquette and Muskegon. Each reach gets three to seven nights before the hatch moves upstream, so the trick is being on the right stretch. Duns emerge at dusk and the spinner fall into darkness is the best fishing; Brown Drakes and Sulphurs drive the evening rise on the South Branch. Fish a #10 Brown Drake dun or spinner, or a Robert's Yellow Drake, and a burrowing-nymph pattern over sand and silt before dark.

The fourth of the Au Sable's Big Five, with a June peak and a second September peak that gives some of the best fall dry-fly fishing. Nymphs are strong swimmers in fast cobble water and crawl out on rocks to emerge, leaving shucks on the stones, so a swum or stripped #10-12 Iso nymph is the primary fish-catcher, and the spinner fall in late evening over moderate current is the surface event. Fall duns often emerge midday and trout do take them on the water; a #12 Adams or Borcher's Drake covers the dun and spinner. Starts the first week of June on the Muskegon and runs sporadically to September.

The second of the Au Sable's Big Five and the bread-and-butter afternoon hatch of late May and June on the northern rivers, with dense hatches on the Pere Marquette that create selective risers in slow glides and tail-outs. Emergence is sporadic through the day with an afternoon-to-evening peak, and spinners drop at sunset. Trout routinely refuse duns during this hatch, so emergers and rusty spinners outfish dun patterns; carry pale yellow, orange and olive shades because body color varies. On the Muskegon and Pere Marquette the hatch runs a size smaller and continues through July.

The last big mayfly of the season: a burrowing mayfly that erupts at dusk from about August 14 through September on the Au Sable, Huron, White and Rifle rivers, with huge numbers emerging after dark. The event is compressed into about two hours; males molt to spinners in flight while females stay as duns, so a single cream-bodied, gray-winged pattern (White Wulff, White Parachute, White Comparadun #12-14) covers it. Bright white flies are inaccurate; the naturals are cream with light gray wings. Get in position before dark and expect a short, frantic rise.