Fly Fishing On The Au Sable Mio to Alcona

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This is “The Big Water” made famous by trophy browns and rainbows and moderate (but increasing) angling pressure. Special angling regulations have been in effect for many years on the run from Mio to McKinley, a distance of about 15 river miles, and the results are impressive. Brown trout over 20 inches are not at all rare and rainbows from 14 to 18 inches are free risers whenever there is a reasonable number of mayflies available as emergers, duns, or spinners.

It is worth mentioning that I fish this stretch most often. Over the course of nearly fifty years on this water, I have rarely seen a trout over 12 inches eat an adult caddis. This is not to say that they do not eat the nymphs, they surely do, but the adult caddis seem to go about their buggy business unthreatened by trout. Perhaps the caddis adults below Mio taste bad. I think the more likely answer is that the fish are truly spoiled and lazy. An adult caddis flutters and darts and might get away. Why waste the energy? Easier prey will be along shortly. Complementing the prolific mayfly hatches are dense populations of crayfish, sculpins, darters, dace, shiners, chubs, and juvenile trout.

The Big Water is logically divided into three sections or floats. The first run is about eight miles from the boat ramp in the town of Mio to the public access at Comins Flats off McKinley Road. This is a lovely, productive stretch of river with pools, runs, riffles, and deep holes. There are only three sites along this course that have cabins visible from the river. The rest of the view is forest, specifically the Huron National Forest. Access is generous and easy along several USFS numbered trails on both the north and south sides of the river.

Early-season angling improves when the water temperature reaches 55 degrees F. It peaks and holds constant at temperatures between 60 and 68 degrees F. The Hendrickson hatch can be spectacular on this water when the peak emergence coincides with the magic 55-degree mark. Other hatches to note are the Sulphurs, brown drakes, Isonychia, and white fly.

The next downstream section is the reach from Comins Flats to McKinley. It is about the same length in terms of river miles but the river’s personality changes a bit. There are more frequent stretches of slow water and there is an attendant build-up of silt. The silt, as you know by now, harbors the Hexagenia limbata and this adds spice to the evening soup.

Below Comins Flats there are several very deep bend holes shaded by heavy foliage. These hold super trout that will often respond to large streamers that mimic sculpins or crayfish. The riffles, particularly where they slow and blend into a pool, hold both rainbows and browns (and, rarely, brook trout) with a seeming predisposition to surface-feed. The best dry-fly action is during the Hendrickson, brown drake, and whitefly hatches, but Sulphurs and mahoganies in late May, and Hex during early June, can produce superb angling.

From McKinley downstream to USFS 4001, the river runs entirely through the Huron National Forest. There are no cabins or structures of any kind on this wilderness float.

The current is a bit slower and there is more silt in this reach, so the numbers of Hexagenia limbata mayflies increase proportionately. Usually the hatch begins about June 12 and continues through the first of July. In addition to the Hex, anglers find the Hendrickson, Sulphur, brown drake, Isonychia, and whitefly hatches rewarding. Large sculpin streamers fool big fish throughout the year, particularly at dawn or dusk, or on heavily overcast days.

Trout anglers will sometimes hook into trophy-sized smallmouth bass on streamers and, more rarely, a large walleye from one of the deep holes in this section.

By Bob Linsenman reprinted with permission from his book the Michigan Blue-Ribon Fly-Fishing Guide