Ohio's coldwater exception
Western Ohio is corn country, and most of its rivers are warm, muddy bass water. The Mad is the exception. It runs 66 miles from its source near Campbell Hill in Logan County through West Liberty and along US 68, past Urbana and Springfield to the Great Miami in downtown Dayton, and it is the largest coldwater fishery in Ohio. It stays cold enough to carry trout through the summer in a part of the state where almost nothing else does.
It is not a wild trout river in the Pennsylvania sense. Natural reproduction is low, blamed on sediment from channelized reaches and farm runoff and on lost habitat, so the fishery depends on stocking.
Five hundred browns a mile, every October
The Division of Wildlife manages the Mad as one of three coldwater streams in its brown trout program. In the district fisheries biologist's 2016 notice announcing a creel survey, the state described stocking yearling browns at about 500 per river mile each year, in early October, usually 6 to 8 inches long but ranging from 4 to 12. A study from 2011 to 2014 tracked survival, growth and movement of those fish, and the April 1 to November 6, 2016 creel survey was the first since 1994, set up to measure total angler effort, the peak trout season, how many fish are kept, and whether stocking draws new anglers. The state periodically stocks rainbows as well.
The October timing matters for planning. Fresh browns are in the river through late fall and winter, and fish that survive a year or two are the ones worth the 12-inch rule below. Ohio Fly Fishing Guides, the guide arm of Mad River Outfitters in Columbus, runs brown trout trips here year round and says some of its best days come in winter. It also says rainbow trout in Ohio are a November to April fish.
Two fish, 12 inches, including the feeder creeks
Ohio's statewide trout limit is five with no size limit, but the Mad River and all its tributaries are a site-specific exception: two trout a day, 12-inch minimum. The same rule covers the Clear Fork of the Mohican in Richland County. The biologist's notice says the rule dates to 2000; before that it was five fish at 10 inches.
There is no closed season. Ohio stream access follows property: the Division of Wildlife's own river maps remind anglers that you may fish only from public land unless you have permission, including the streambed where it crosses private ground. Stick to public access and bridges unless you know the owner.
Where people actually fish
Guided trips concentrate near Urbana, and Ohio Fly Fishing Guides floats the Mad in drift-boat rafts as well as walking it. The USGS gauges line up with the popular reaches: West Liberty in the upper river, Urbana, St. Paris Pike at Eagle City, then Springfield and Dayton below. Mad River Outfitters' founder, Brian Flechsig, started guiding on this river in 1989 and still floats it in an Au Sable River boat on request.
Urbana gauge: small numbers, big changes
No shop posts a wading range for the Mad, so the 90 to 250 cfs band here comes from the USGS record at Urbana. Monthly means sit around 245 cfs in March and April, 184 in June, and about 91 to 110 cfs from August through November. In the three weeks to September 23, 2026 the gauge ran from 156 to 1,090 cfs after a storm and read about 312 on the 23rd, high and likely stained for a spring creek. After a spike that size, give the river a few days and watch the gauge fall back toward the low 200s before driving over.
The river grows fast downstream. On September 24, 2026 the West Liberty gauge read about 68 cfs, Urbana 279, Eagle City 409, Springfield 622 and Dayton 926, and Wikipedia puts the long-term average at Dayton near 757 cfs. If you are fishing the upper river around West Liberty, check that gauge rather than Urbana, because the headwater reach runs at a fraction of the flow and wades very differently.
Small bugs and a winter season
Nobody publishes a dated hatch chart for the Mad. The table uses a published eastern freestone chart for timing: midges through the cold months, blue-winged olives in spring and fall, caddis and sulphurs in May and June, then terrestrials along the grassy banks in summer. Scuds and sculpin patterns fish all year for the stocked browns.