March brown
Also called March Browns, March Brown hatch
“March brown” is a common name for several medium-to-large spring mayflies and the hatch events tied to them. The name can mean different species depending on region.
- Group
- Mayfly hatches
- Category
- Entomology & forage
- Level
- Intermediate
- Water
- Freshwater
Last updated
What March brown means
On many trout rivers, “March brown” refers to early-to-mid spring mayflies in the genus Rhithrogena (and sometimes similar-looking species grouped under the same common name). Anglers use the term for the whole cycle: nymphs, emergers, duns, and spinners.
The hatch is often associated with faster water—riffles and runs—because these mayflies are strong swimmers and clingers. On the water, the most consistent fishing is frequently subsurface with nymphs and emergers, with shorter windows of steady dry-fly action when duns are coming off or spinners return.
Because “March brown” is a common name, timing and size vary by watershed. In some places it’s a headline spring hatch; in others it’s a minor event mixed in with other mayflies. Matching the stage (nymph vs. emerger vs. dun vs. spinner) usually matters more than matching a single exact pattern name.
Why it matters on the water
Knowing what “March brown” means in a specific river keeps the plan simple. If the shop report says March browns and the surface looks quiet, that points toward a nymph or emerger approach in riffles instead of waiting on a dry bite that may only show up in short bursts.
It also helps with fly selection and leader choices. March brown adults are not tiny, and they often show in broken water, where a slightly more visible dry or a soft-hackle-style emerger can be easier to track and fish effectively than a small, low-riding pattern.
Read next
- Green drakeA “green drake” is a large mayfly hatch that can bring trout to the surface for big dry flies, especially in late spring and early summer. The name is used for several similar-looking mayfly species depending on the region.
- HendricksonA Hendrickson is a spring mayfly hatch best known on Eastern trout rivers. Anglers use the name for the insects and for fly patterns that match their duns and spinners.
- Soft hackleA soft hackle is a lightly dressed wet fly with a soft, swept-back feather collar that pulses in the current. It’s fished under the surface to suggest an emerging insect or a small drifting bug.
- SpinnerA spinner is a dry fly that imitates an adult mayfly after it has mated and fallen spent on the water, usually with wings laid flat to the sides.