Western March Brown

Photo by Les Korcala

March Brown Overview

  • Family: Mayfly
  • Size: 10-12mm. (Size 12-14)
  • Emergence: Late March through runoff
  • Emergence time: Afternoon

The Western March Brown hatch in Montana is the first sizable mayfly hatch, appearing in late March and going through runoff around Missoula.

Where and What To Fish

Mostly known on the Bitterroot River, they are excellent on Rock Creek and the Clark Fork River. Look for the WMB’s to appear in the afternoons, and they like the warmer weather. When you’re looking for Skwalas, but find fish rising consistently in April, they’re probably on Western March Browns.

The WMB is prolific, but not a blanket hatch. It’s not always critical to have a wide range of flies to match this hatch. Often a parachute and a cripple are all you need to get the fish to move. It’s nice that way!

March Brown Nymph

Sub-surface, the nymphs are well known. A basic Hare’s Ear or G Kes perdigon can be a strong producer, especially a little off the shore. The mid river fish aren’t seeing many Skwala or Nemoura nymphs, so they’re looking for the WMB and BWO nymphs.

Fun Fact

As an aside, the Western March Brown is a bit of a misnomer, and harkens back to the British origins of American fly fishing. The British have a true March Brown, a mayfly that hatches in March. The Western March Brown is a bit more tan, and doesn’t really establish often until April. But because the name was established, they just slapped Western in front, and called it good!

Additional Western March Brown Resources