March Brown Mayflies

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March Brown Mayflies

Main article by: Rick Hafele, with some pictures and comments by Mark Bachmann

The other day (3/15) March Browns were emerging from one of the local steelhead rivers and the trout were up after them. Some of the trout were large enough to make very showy rises. The dun pictured below landed on my boat seat and got her picture taken with my iPhone11 Pro. Cell phone cameras have become more and more amazing. In many ways it is hard to distinguish the picture from one taken with a DSLR with an expensive macro lens. 

Often there are two different kinds of mayflies emerging from our wester rivers at the same time, those that emerge from the bottom to the surface of a river and the kind that crawl out onto rocks (blue background above article title). They look nearly identical but the ones that emerge mid-river produce rising trout, and the ones that crawl out go unnoticed by fish.

Rhithrogena morrisoni (that's the scientific name) of the mottled wing brown early spring may fly that feed rising trout. Western March Browns (or simply March Browns) are your first "easy-to-see" mayfly hatch of the new season. Look for March Brown hatches on local rivers when water temperatures start reaching 42 degrees consistently. They often get stronger as water temperatures approach 47. This can occur in most lower elevation water sheds in mid-February and continues through March and early April.

Hatching March Browns can create some very exciting surface film and dry fly fishing. Hatches of duns usually start in the early afternoon and spinner falls are in the late evening. Pounding the bottom with a weighted March Brown Nymph can provide constant action from mid-morning into the early stages of the hatch. Most are fairly skinny #14's, but slightly larger flies can also work. The March Brown Nymph in sizes #12 and #14, or a Pheasant Tail Nymph of the same size, will be your bread and butter flies.

March Brown nymphs are flat hydrodynamic shaped clinger/crawlers with an underside that is cupped, with the gill plates forming a sucker to help hold the nymph to rocks in extremely fast water.

Nymphal color tends to adapt to the color of the stream bed. Most March Brown nymphs are dark, some are nearly black. Your catch may increase if you thin out the legs with your leader clipper and color them with a black felt marker.

Fishing two flies at once will increase your odds of hooking up. Usually two different colors or sizes are used. The Guides Choice Hares Ear is a valuable pattern to have with you, and will sometimes out-fish the more realistic patterns.

March Brown nymphs live in riffles and fast, rocky runs. As the nymphs near maturity, they migrate to slower water. During the migration, they can lose their grip and drift in the current. For this reason, trout will congregate in places where fast riffles start to slow down and on the seams between the fast and slow water. Fish your nymphs where the current changes speed.

Approach the water carefully. Start by fishing the slower water first with flies that are lightly weighted. Your flies will be most effective if they are perfectly dead drift. Cast them slightly upstream and mend a little slack into your presentation. As you work your way out into the faster current, add lead shot to keep your flies near the bottom.

As the water warms at mid-day the nymphs rise toward the surface to hatch. Some of these nymphs are intercepted by trout during this upward migration. Try tying a March Brown Soft Hackle to a dropper 3' above your nymphs. This technique can pay extra dividends.

Swinging soft hackle emergers during the early stages of the hatch can also be deadly effective and lots of fun. As the duns begin to hatch, trout will rise to the surface to catch them. This often produces the most visually exciting part of the day. Big trout rising to March Browns during the peak of the hatch can be very splashy. Often the rise starts much quieter as trout pick off the emergers just below the surface. And some duns will emerge from the shuck slightly below the surface. At this time, a Soft Hackle fished just below the surface can be your best fly. The soft hackle is often even more effective if you add a March Brown dry fly to a dropper 1' to 3' from your soft hackle and fish both flies dead drift.

March Browns and their possible related species seem to come in a variety of shades and colors. That is why there is some disagreement between anglers fishing different watersheds as to what the actual colors of March Brown Duns are. The ones that hatch most often on the Sandy River are brown with mottled wings. We have seen that same fly on the Deschutes and Clackamas Rivers. On the Deschutes, we have also seen spring time mottled wing mayflies that were grey wing olive. The trout like both kinds. Our friends that fish the McKenzie report March Browns that are shades of gray. To be on the safe side you should carry several brown patterns, a blue wing olive parachute and a Parachute Adams in dark tones. If they are all #14 you're probably in the game.

Duns and emergers produce the best fishing, but some trout will sip spinners in the quietest of water. A March Brown "spinner fall" can extend your fishing day. Spinner falls usually occur over faster water areas. However, they create the most reliable feeding activity if they raft up in back eddies downstream. Sometimes the afternoon back eddy rise that you think is midge emergence is actually created by collecting dead March Brown spinners.

The best tackle to fish the March Browns is a 9' #4 or #5 weight rod with an action that works easiest at the 20' to 50' cast range. I prefer a weight forward line that is a little on the heavy side, is a moderate color, and is very clean so that it easily shoots smoothly at all ranges. The standard 9'-5X trout leader is a good starting point. You might go to 4X if you get brutalized by big fish. Remember the best fly is the one that is perfectly placed in a risers feeding lane.

Have a great spring!

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