Is the Au Sable River good for rainbow trout?

Yes, with a caveat. Michigan's own survey records list rainbow trout in the Au Sable River, and stocks it as well, and the river's measured July mean of 70.2 °F runs above the 55–65 °F this fish prefers but below the 75 °F it stops feeding at — so the cold stretches carry it and the warm ones are marginal in high summer. Across 8 gauged stretches the July mean runs 66.3–75.5 °F, so the answer changes with where you stand on it. Fish of 8–16 inches are what Michigan reports as typical. The river is designated Type 1, Type 2, Type 3 and Type 4 trout water, which is what sets the size and creel limits.

Open Au Sable River on the map See Au Sable River on the live map → Every reach coloured by water temperature, with the public land and access points along it.

What the state's records say

Species: Rainbow trout (Oncorhynchus mykiss)
In Michigan: introduced
Record here: surveyed present, and stocked
Holds in: 55–65 °F, stops feeding above 75 °F
Typical: 8–16 inches
Spawns: Spring — March into May — on gravel, which is what separates it from the two autumn spawners above.

Introduced from Pacific-slope stock in the 1880s. The lake-run form — steelhead — is the same species, and the rivers that hold resident rainbows are largely the rivers steelhead run.

Is the water cold enough

Measured, not modelled: 8 gauged stretches of this river average 70.2 °F in July (66.3–75.5 °F across them), against the 55–65 °F this fish holds in and the 75 °F it stops feeding at.

Gauge	Now	July mean
Red Oak	56.3 °F	66.3 °F
Mio	57.6 °F	70.0 °F
Mc Kinley	56.1 °F	69.5 °F
Curtisville	57.4 °F	71.8 °F
South Branch	60.4 °F	74.0 °F
Glennie	60.6 °F	74.1 °F
Sidtown	63.5 °F	75.4 °F
Au Sable	64.8 °F	75.5 °F

What you may keep

Reach type	Miles	Minimum	Season
Type 1 Designated	15.1	10″	Last Saturday in April–September 30th
Type 2 Designated	13.0	10″	Last Saturday in April–September 30th
Type 4 Designated	27.3	10″	January 1st–December 31st
Type 3 Designated	12.1	10″	January 1st–December 31st

From Michigan's own regulation tables, per designated type, and the current digest is the authority rather than this page. Full regulations for this river →

What to fish for it

Fish Eggs — October–January and April, #10–16
Little Black Stonefly — January–April, #16–18
Little Brown Stonefly — February–April, #12–16
Blue-Winged Olive — March–May and September–November, #16–22
Blackfly — April–June, #18–22
Blue Quill — April–May, #16–18
Cranefly — April–June and September–October, #6–10
Grannom — April–May, #14–16

The insects recorded from this river's region, earliest first. The full calendar →

More about Au Sable River

Au Sable River — live water temperature, regulations and access

Nearby rivers for rainbow trout

Houghton Creek 5.8 mi