March Brown
Imitates: March Brown mayfly dun (Maccaffertium vicarium)
Quick Reference
- Best Sizes
- #10-14
- Best Season
- Late April through early June — first big hatch of spring in the East
- Best Conditions
- Cool overcast afternoons, riffled water, 50-60°F water
- Water Temp
- 50-62°F
- Recommended Tippet
- 4X-5X nylon
How to Rig It
Single dry on a 9-foot leader, or trail a March Brown wet fly 18" behind on the swing.
How to Present It
Cast across and slightly down, let it drift through riffles and into the head of the pool. A subtle twitch at the end of the drift triggers strikes.
Why It Works
March Browns are big mayflies (#10-12) that hatch sporadically all afternoon — fish don't get filled up, so they keep eating. The mottled wing and brown body match the natural exactly.
History
Named for the British March Brown, but the American version (Maccaffertium vicarium) hatches in May, not March. A Catskill-tradition pattern dating to the late 1800s.
Pro Tip
Fish March Browns 'sloppy' — slap the cast hard and let it skate momentarily before the dead drift. Naturals are awkward fliers and fish know it.
Frequently Asked Questions
When do March Browns hatch?+
Late April through early June in the Eastern U.S., with a peak window of mid-May. Western March Browns (Rhithrogena morrisoni) hatch March-April on the West Coast.
Is the March Brown an Eastern or Western hatch?+
Both — but the species and timing differ. Eastern is bigger and hatches in May; Western is smaller and hatches in early spring.
Not sure if March Brown is right today?
Get a fly recommendation based on live water temp, flow, sky, and time of day for any river in the US.
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