Spring is here. That means it’s March Brown time.

I saw a small hatch on the river last week. Here is one of them.

March Brown Adult | www.johnkreft.com

I think it’s early, but our weather has been so mild I’m really not surprised. In fact, I was looking for them. I took one of my bug vials filled with Purel hand soap with me just in case. I’m glad I did. I take these back to my fly tying bench to match color and size.

March Brown - Vial | www.johnkreft.com

Western March Brown mayflies (Rhithrogena morrisoni) are in the #12 – 14 size range. If you look at them from above, they appear a medium to dark brown. But that’s not what the fish see. The fly’s abdomen where I live is a reddish-brown. They might be different in the waters you fish. And their wings are very distinct…brown and mottled or some fly fishers would call it cathedral window-like. 

I’ve seen some caddis fluttering around on my home waters, but this is the first major mayfly bigger than a #18 or #20 Blue Wing Olive to begin hatching. Perhaps the fish will think it’s spring and start rising more. I hope so.

Before I present a few flies, let me provide a brief description of a March Brown’s life-cycle.

Like all aquatic insects, it begins with an egg. The egg hatches and becomes a nymph, living in fast, clean water. The March Brown nymph is known as a clinger because it attaches itself to the bottom of the river by it’s gills, which act like suction cups. Meals consist of algae scraped off the rocks where the nymph lives and grows.

After living in the river for about a year, it’s time to hatch. The nymph swims to the surface and escapes the nymphal shuck. And the adult, or dun as their known, flies away.

The dun lives along trees and brush waiting as it sexually matures, molting again into the spinner phase. After mating and laying eggs, spinners fall into the water where trout may feed upon them.

Nymph, emergers, and adults are all important to the fly fisher. All phases are easily imitated with the flies listed below.

I’ve seen a few good hatches. I was floating on the McKenzie River in a drift boat several years ago and observed nymphs swimming to the surface, pausing briefly while the dun climbed out of the nymphal shuck and flew away. It happened so fast, I didn’t have time to reach down and grab one to get a closer look. I’m guessing that’s why trout rise with purpose. They don’t want the dun to get away. 

If you would like to get more information about March Browns or any other aquatic insect, I highly recommend the book BugWater by Arlen Thomason. It’s a favorite of mine. Another great resource is Western Mayfly Hatches: From the Rockies to the Pacific by Rick Haefle and Dave Hughes. If you get a chance, be sure to check them out on my Fly Fishing and Fly Tying Books page.

So the question is, what flies should you use to imitate these important phases?

Well, let’s start with a couple of nymphs and work to the adult stage.


You know I like simple flies, so here are a couple of nymphs that should work for you.

Fish these patterns anytime of year, but especially now when they’re more active. And fish them in the upper part of the water column when the hatch starts, as fish are used to see them swim to the surface.


Then there’s the transitional phase where the nymph swims to the surface and hatches. Fish are actively searching for easy prey and these flies should work.

I like to use a old style wet fly soft hackle for this phase…and it works for me.

Pheasant Tail Soft Hackle

Pheasant Tail Soft Hackle | www.johnkreft.com


Cripples are adult insects with their wings caught in the surface film or stuck in the nymphal shuck. Many mayflies have difficulty escaping the nymphal shuck. And when they do, one or both wings may stick to the water, preventing their flight. I like my RiverKeeper Soft Hackle Cripple to imitate this phase.

RiverKeeper Soft Hackle Cripple

RiverKeeper Soft Hackle Cripple - March Brown | www.johnkreft.com

Or another favorite…

March Brown Sparkle Dun

Duns (adults)

I use several flies to imitate the adult stage where the March Brown mayfly floats on top of the water as it drifts downstream before taking flight.

March Brown Parachute

March Brown Parachute | www.johnkreft.com

March Brown Comparadun

Comparadun - Mahogany | www.johnkreft.com

Several years ago, I had a tremendous day of fishing on the Middle Deschutes. I was lucky enough to hit a March Brown hatch that happened to last several hours. The fish weren’t huge, but they were a mixture of Browns and Rainbows…and I caught a lot of fish! What fly did I use? A March Brown Comparadun…a simple fly. While I fish its cousin the Sparkle Dun, I’ll never forget how the Comparadun worked so well.

Parachute Adams 

Parachute Adams | www.johnkreft.com

I’m always amazed how well this older fly works. It seems to imitate any mayfly as long as the fly is similar in size. Kinda goes against my theory of matching body colors, but the fish are smarter than I am! I invite you to check out one of the Throw Back Thursday Flies page for a little history of the Parachute Adams.

Mel’s McKenzie Mayfly 

Mel's McKenzie Mayfly | www.johnkreft.com

My friend Jeff Perin, owner of The Fly Fisher’s Place in Sister, Oregon, shared this fly with me. It’s fun to tie and just looks cool. Try one.

So there you have it…a brief description of the Western March Brown along with some fly patterns for you to try.

March Browns | www.johnkreft.com

I hope March Brown time will be a favorite time of year for you.

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