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Brown Drakes

Jeff Morgan


Brown drake hatches don't happen everywhere, and they can be notoriously elusive. But one it happens, it's an event you don't want to miss.


 

Images

(See the entomology page for photos)

Brown drakes are responsible for some spectacular evening emergences on many rivers, such as Idaho's Henry's Fork and Oregon's Williamson, where the large size of the dun brings the heftiest trout to the surface. The brown drake can also be found in lakes, and while I might not know of any examples to offer, it may be because the locals keep these spots a tightly guarded secret.

The brown drake family only has one prominent member in the West, Ephemera simulans. Ernest Schwiebert in his book Nymphs, mentions another western brown drake found in Colorado, E. compar, as being important to flyfishers. However, this insect is only known by one adult specimen, which was collected in 1874, and entomologists know of no other specimens since then.

Nymphs

With that taxonomic nonsense clarified, let's consider the insect. First, the brown drake nymph is usually not brown, but rather a pale tan or yellow--the kind of pasty appearance you'd expect from a bug that spends most of its life underground. The nymph is about 14-21 mm in length and has large gills adorning its abdomen. Nymphs breathe by a rhythmic undulation of their abdomen, causing water to flow through the plumes of gills.

Brown drake nymphs are burrowers. They seek out a sand or fine gravel substrate, then dig into it. This is a distinctly different substrate than is utilized by that other preeminent burrower, Hexegenia limbata, which prefers a clay or mud bottom.

Brown drake nymphs often bury themselves 4-10 inches into the substrate, thus remaining beyond the reach of fly anglers seeking samples. I have screened the Gibbon River in Yellowstone Park a few times, and have found not one brown drake nymph. Yet they are a major event on the river.

The brown drake nymph resides in its burrow and remains hidden throughout the daylight hours, but moves out to actively hunt other insects under cover of darkness. This is a distinctly different feeding behavior than Hexagenia limbata, which feeds on decaying vegetation. Because of its active nature, imitation of the brown drake nymph can be productive where night fishing is legal.

Emergence

Nymphs mature in about one year. When ready to hatch, the nymph leaves its burrow and rushes to the surface. Its swimming motion is quite acute and is performed with a rapid undulation of the abdomen. In their classic book Fishing Yellowstone Hatches, Craig Matthews and John Juracek doubt the importance of this motion to the angler, noting that attempts to imitate this motion, either by material or design, were largely futile. Considering the inspired tying that emanates from their fly shop, their statement carries a lot of weight.

The twilight emergence of brown drakes can be an amazing sight. Many people compare it to the Hexagenia hatch. Both insects emerge in the evening in dense numbers as a biological adaptation to elude actively feeding trout. Though they do emerge throughout the day in other locals, western emergences are restricted to the gloaming. Emergence may also occur on overcast days. Most emergences occur in June through early July.

Adults

After a year of nymphal repression, the brown drake duns are usually avid lovers. Mating begins shortly after emergence, often near shoreline vegetation. Within a day or two, swarms of males may congregate over the water, but this may not be indicative of a good spinner fall. Females brown drakes will drop their eggs from above the surface, then fall spent to the surface soon afterwards. Adults usually live less than 72 hours.

Tactics

The nymph of the brown drake is of limited interest to fly anglers, for it spends most of its life buried in the mud. However, if you're fishing right at dusk or at night in slow-water areas, it may pay to carry a few nymph imitations. Try dead-drifting one through slow water, then swimming it (with short strips of line or a short raising of the rod tip) toward the surface at the end of the drift. Trout will follow the nymphs all the way to the surface, so pay attention to your line as long as your nymph is in the water.

A tan or creamish-yellow nymph in a size 8-10, is what you want to shoot for. Since these insects swim with a vigorous side-to-side motion and have very fluffy gills all along their sides, common sense would dictate that you should use materials that imitate all this motion, like marabou, ostrich herl, or rabbit fur. As mentioned before, however, this hasn't proven to be the case and nymph patterns are of little value.

The same cannot be said for adult imitations, though. They are very important if you concentrate on the brief evening emergence period. Look for trout rising in slow water, where they will take up cruising patterns and slowly move upstream. When you see this happening, it is important to cast your fly only 2 feet in front of a rise. Any farther and the fish may have moved to the side before your fly reaches it. The trout in this slow water are often very spooky, so let the trout start to rise consistently before you bombard them with the big dry flies.

When choosing a pattern to imitate the brown drake dun, look for ones that will still float well, even when burdened with the weight of a size 8 hook. Foam-bodied Bunse Duns and extended-body brown Paradrakes are good choices. You want to make sure the flies floats well because they can be tough to see in the low light if they are just hanging in the surface film.

Jeff Morgan has written many articles for Westfly, mostly on entomology and fly tying. He is the author of An Angler's Guide to the Oregon Cascades and Small Stream Fly Fishing. Jeff is currently a graduate student at Stanford University, where he is finishing his PhD in History.

Uploaded 06/03/2001.


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