Eastern March Browns
Living in the East, I’ve witnessed phenomenal mayfly hatches. Many of them have faded into the murkiness of memory, and I’m sure that many more have been entirely forgotten. But the hatch I best remember occurred on the Beaverkill’s most heavily fished water, Cairns Pool.
It was a rare spring day—one that provided a break from managing the fly shop—and I desperately wanted to find mayflies and rising trout. But the weather was not cooperating. Melting snow and heavy spring rains had swollen the local rivers to near flood stage. So I was out for a drive, hoping that just being near the water would mitigate the longing for trout fishing that a hard Catskill winter fosters in its residents.
I steered my car into the pull-off at the head of Cairns Pool, and as I stepped out for a look, I saw large mayflies struggling in the heavy currents, flopping and falling as they attempted to escape the roiling water. Potentially drowning in the swollen river wasn’t the emerging March Brown duns’ only concern; several acrobatic brown trout were forcefully slashing through the currents, ravenously grabbing flies before the water swept them beyond reach.
Though the high water kept me from fishing, I’ll never forget how enthusiastically the trout pursued those March Browns.
Misinformation
March Brown emergence is one of the East’s best hatches, yet a great deal of misinformation and controversy surrounds it. Angling writers often include the Eastern March Brown on their lists of “super hatches.”
This lofty status could give some anglers the impression that March Browns appear in the same water-blanketing numbers as some other spring mayflies. They do not. March Browns usually emerge in a trickle through the day, often beginning in late morning and continuing through the afternoon. Once trout notice the hatch, they become keenly aware and pursue this mayfly through all its lifecycle stages.
This amplified trout awareness, combined with a relatively sporadic hatch, creates perfect conditions for blind-casting drys to likely trout holding spots. In fact, blind casting drys and emergers is often the most productive technique during, and for a brief time after, a March Brown emergence.
Although finding trout rhythmically feeding on March Brown duns is rare, it does happen. I had a wonderful, rainy afternoon this past spring when the fish actively fed on March Brown duns. But you should never expect that kind of trout activity with this hatch. Be prepared to blind-cast your flies, or wait for the mythical March Brown spinner fall.
The hype surrounding its super hatch status isn’t the only misleading March Brown information. Even the common name, “March” Brown, is a misnomer, considering they usually hatch in May.
So how did they get their name? Fly-fishing experiences in Europe helped pioneering American fly fishers understand the new insects and trout they encountered in North America. Eastern March Browns (Maccaffertium vicarium) closely resemble the European species Rhitrogena germanica. These brownish European mayflies hatch in March, so anglers there gave them the common name March Browns. When anglers in the New World encountered the similar-looking M. vicarium, they adopted the same name.
But as American entomologists expanded their studies at home, new ideas and opinions were formed. For many years, March Brown taxonomy was Stenonema vicarium. Another mayfly, commonly called Grey Fox by anglers, was listed as a separate species, Stenonema fuscum. Today, science tells us that March Browns and Grey Foxes are actually minor variations of the same species—commonly separated by size. And the mayfly once known as the Grey Fox (S. fuscum) has now been reclassified out of existence.
The former March Brown genus, Stenonema, has also been replaced by Maccaffertium, named after Purdue University’s professor of aquatic entomology, Patrick McCafferty. McCafferty recently sent me an e-mail stating, “M. vicarium has been a major source of taxonomic confusion because of the range of variability in both nymph and adults.” So if professional entomologists have struggled with the differences and similarities between March Browns and Grey Foxes, it’s not surprising that fly fishers are also confused.
Prominent Penn State University entomologist Greg Hoover has his own strong opinions on the Grey Fox/March Brown debate. Hoover says that many of the mayflies anglers call Grey Foxes aren’t really March Browns (M. vicarium) at all, but rather Maccaffertium ithaca, or Light Cahills.
The March Brown/Grey Fox debate, though important, is largely a scientific exercise. Some amateur angler-entomologists still argue that the two species should be separated. But professional entomologists’ classifications stick. Nonetheless, there are angler-important differences between mid-May March Brown hatches and emergences of the smaller, March Brown-looking mayflies that hatch from late May through mid-July.
Early and Late
By the time the March Browns arrive, anglers have already been fishing hatches of small- to medium-size mayflies such as Hendricksons and Blue-winged Olives for up to two months. But the first March Browns of the year are huge in comparison. March Browns in fertile waters can easily fill #8, 2X-long hooks and the small ones are #10.
Early March Browns begin hatching in mid-May when the water is often still cold, and they appear during the warmest part of the day, usually from late morning through the afternoon. These mayflies continue hatching through the end of May and often overlap with big Sulphurs (Ephemerella invaria), the beginning of the Green Drakes (E. guttulata), and the insects fly fishers call Grey Foxes.
Grey Foxes begin hatching near the end of May and can continue sporadically until mid-July. The flies—nearly identical to their earlier arriving brethren—look like shrunken, sun-bleached, #12-14 versions of the larger mid-May flies. The name Grey Fox implies that the flies are gray, and many tiers use light gray materials for the wings or body. But I’ve never encountered a Grey Fox that actually looked gray. Most of them range from pale tan to cream, with light brown markings on their legs and backs. Grey Foxes usually emerge in the coolness of the evening because the water has warmed, similar to emergences of the various Cahill species. Grey Fox hatches often overlap with Slate Drakes (Isonychia bicolor), little Sulphurs (E. dorothea dorothea), big Blue-winged Olives (Drunella cornuta), and Light and Cream Cahills (Stenonema interpunctatum interpunctatum and M. modestum) during their long emergence period. [Aquatic insect body coloration can vary greatly from stream to stream, so the color descriptions given here for the nymphs, duns, and spinners are basic guidelines. Examine March Browns from your own waters to find the colors that most appropriately match the hatch. The Editor.]
Nymphs
March Brown nymphs are in the family of clingers. They are usually found holding on to the bottoms of rocks in riffles and swift-moving glides. Nymphs have three tails and reddish-brown to dark, blackish-brown bodies, with darkly ribbed amber abdomens. Their wingpads and legs are also dark brown, but lighter-colored mottling on the legs is prominent.
March Brown nymphs have wide, flat bodies. Use a flattened tungsten or lead wire underbody to make your nymphs appear like the naturals. March Brown nymphs migrate from fast water to slack areas around boulders and near the shore, or even slow pools, to emerge during high-water conditions. But if the stream flow is low, it’s common to find them emerging in riffles.
You don’t need to wait until you see the first March Browns hatch to fish the nymphs. Trout start feeding on them in early May about a week or so before the hatch commences, when the bugs begin migrating to emergence areas.
Dead-drifting #8-10 nymphs in the riffles is productive, but slowly stripping the flies toward shore, like a streamer, can be better, particularly if the water is high.
I’ve also caught a lot of trout with March Brown wets [see recipe]. Fish these flies with a traditional down-and-across swing, or dead-drifted on a leader weighted with split-shot. From late May through mid-July, fish smaller nymphs and wets (#12-14) to imitate Grey Foxes.
Copyright © 2012 Intermedia Outdoors
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