March Browns: A Trouts First Real Meal

Getting you ready for the Pacific Northwest March Brown hatch

What are these springtime bugs, and why should you care?

 

March Browns (Rhithrogena morrisoni) are a subspecies of mayfly found in the Western United States. These tasty midsized bugs represent our first real opportunity at consistent dry fly action in the Pacific Northwest each spring. Between their chunky size, favorable flavor profile, and timing, March Browns can be one of the most exciting and underrated hatches in Oregon.

 

Coming out of a long, lean winter, the fish are hungry, and most haven’t seen a dry fly cast their way in many months. Their behavior is similar to lake-bound trout after spring ice-off — aggressive and a bit reckless, with the biggest specimens coming out to play more frequently than usual. This is one of our favorite times of year to guide for trout, and you can still take advantage of our “Get what you get” offseason special this month to bring the price down. 

When do March Browns show up in the Pacific Northwest?

March Browns need nice, warm weather to get their cycle started and will usually begin to arrive on the scene as overnight temperatures stay in the 40s with regularity and daytime temps jump into the 50s. Once they’re going, March Browns love a stormy, chilly day. You’ll often find the thickest hatches and most willing fish on days with scattered rain showers throughout. Clouds are always a helpful companion when fishing dries, so if you see rain in the forecast, don’t let it deter you. Layer up and be ready for action!

March Browns typically arrive in two different waves, depending on which part of Oregon you prefer to fish. West of the Cascades, both in the Willamette Valley and Coast Range, March Browns are right on time and line up precisely with their namesake month. During particularly mild winters, you might even find March Browns hatching away happily as early as late February — particularly at low altitudes. It takes very little time for these fish to key in on a food source because Willamette Valley streams have more limited food than Central Oregon waters. By mid-April, the hatch tends to taper off.

East of the Cascades, March Browns arrive about a month later, and the best action will be found in April. The bugs need to be there for at least a few days before the fish start looking up with regularity.  Once the fish key in, you can find good March Brown fishing through April and into early May.

Water Type and Techniques 

March Browns tend to hatch in long, wide flats (tailouts) and shallow, mid-speed riffles, starting between 1 and 3 pm. You’ll almost always find trout feeding on these bugs in moving current, which gives the fish less time to inspect your offering — an advantage for the angler. Like most mayflies, they hatch in pulses, ever-present throughout a specific window, but getting thicker and heavier in waves. If you start to see the hatch seemingly die off after half an hour, don’t worry. Just wait.

I tend to fish March Browns as a double dry fly rig, which serves a few purposes. First of all, it allows me to fish two identical flies of different sizes, or two patterns with slightly different coloration, to better understand what the fish are keyed in on. A double dry rig will also indicate beyond any doubt whether or not you are getting a good drift — if your bottom fly is leading the charge, you’re presenting your fly naturally. If not, you have a micro-drift impacting your leader and will catch fewer fish.

To most effectively fish this set-up, cast beyond your intended target directly across and drag and drop your flies so that they are presented exactly the way you want them by the time they drift over the fish. A standard 9-foot 5x tapered leader with 18 inches of 5x or 6x tippet to your second fly will work just fine.

While nymphing before or after a March Brown hatch can be hit and miss, swinging wet flies can be even more fun and deadly than targeting fish on top. Using the same tapered 9x leader, you can swing a bushy March Brown soft hackle on a floating line with a single-hand rod and encounter some of the biggest fish you’ll see all year. 

Fly Presentation and Patterns

If you’re fishing March Browns on a food-abundant stream like the McKenzie or Middle Deschutes, you’ll need to wait until bugs are actively hatching and fish are rising before you can successfully target them on top. During a heavy hatch, be sure to identify rising fish and cast to them with purpose. Once you’re dialed into the rhythm of the rising fish, they become much easier to catch.

If you are fishing a less abundant Willamette Valley stream, like the Luckiamute River, fish a March Brown the way you would on any small stream — dabbing behind pockets and along soft seams to coax fish to the surface. In these environments, fish won’t pass up a meal if it’s well-presented, regardless of whether there’s an active hatch occurring. 

There are also differences in insect size, color and profile of east vs. west of the Pacific Crest. East, March Browns have a more “traditional” look — big bugs with dark, almost mahogany bodies. You’ll want to fish these in a size 10 or 12, and darker patterns like a March Brown Parachute Adams will be most effective. To the west, the bugs are much smaller and lighter in color and are better replicated by Catskill style mayfly dries in cream, pink, tan and light brown colorations between size 14-16. A striped brown thorax is also deadly in the Willamette Valley.

 

Fly Rods, Reels, and Lines

While a three or five-weight will also work just fine in most situations, we find the ideal rod for March Brown fishing to be a 9’ four-weight, with enough backbone to cast into the wind while delicately presenting flies to actively feeding trout. This smaller, more compact rod really comes in handy when you’re fishing March Browns down in the Middle Deschutes canyon, or one of the eastern Willamette Valley’s small year-round streams. The extra length on this rod — most four weights are made in 8’6” models — will give you a bit of additional reach when you’re swinging soft hackles.

A weight-forward or double taper floating line to match your rod will be all you need to fish either presentation, whichever you prefer. Your reel doesn’t need to be fancy, but be sure it has a trustworthy drag function and low startup inertia to let a big fish peel line without snapping your light tippet.

Of course, if you find yourself fishing March Browns on the Lower Deschutes — where you may well encounter 18-inch fish in water blasting through at 4500 CFS — you’ll probably want to upgrade to your trusty 9” 5 weight for dries, and perhaps a 3 or 4 weight trout spey with matching line and a light intermediate sink tip to swing soft hackles. 

Fly Fishing Guide Trips

Want to get out and fish the March Brown hatch with one of the incredible guides on our pro staff? The Lower Deschutes and Lower McKenzie rivers all provide fantastic March Brown fishing starting as early as March 1 and typically lasting through the end of April. Book your trip today to reserve a spot!

About Joseph Beare

Joseph Beare is a guide for Northwest Fly Fishing Outfitters and a regular contributor to the NWFFO blog and newsletter. A former sports reporter, Joseph has been telling stories about outdoor and athletic endeavors for more than 20 years. As a guide, he specializes in unique trout trips, including local year-round water in winter, alpine expeditions on Mount Hood in summer and spring, and searun cutthroat floats in the fall. You can find him on Instagram @pdxflycollective.

Santiam Brown: March Brown Pattern

Hook: Barbless Dry #12-14

Thread: Olive-Brown Danville 6/0

Tail: Golden Pheasant Tail

Body: Golden Pheasant Tail

Ribbing: 6X or 7X tippet (optional)

Thorax: Pheasant Tail Ice Dub

Hackle: Brown or brown grizzly

Fore Hackle: Brown partridge