Fly Fishing Brown Drake Hatches

In tall grass by the water's edge, they wait. It is 8 P.M. during the longest days of the year, and it will be more than two hours before darkness envelopes the vast meadow. Two hundred yards upstream, a half dozen cow elk coax their month-old calves across a shallow riffle and the rasping calls of a nesting pair of sandhill cranes shatter the quiet of an early summer evening on the Henry's Fork.

Alone or in groups of two or three, a dozen or so anglers are scattered on both sides of a wide flat that stretches more than a half mile in length. The water is quiet except for the occasional dimple of a small trout, but even something larger would not cause distraction from the anticipated event that will soon follow.

As the temperature begins to cool and the sun gradually loses intensity, the dance begins. Gracefully rising and dipping over streamside vegetation, the big mayfly spinners signal the beginning of a fly-fishing drama that will be played out past sunset, and on some occasions well into darkness.

Giant Mayflies

Ephemera simulans–commonly known as Brown Drakes–are among the largest mayflies in the Rocky Mountain West, and they populate waters throughout much of the continental United States. In most areas they are a late spring or early summer hatch that can last for as little as a few days to more than two weeks.

On the Henry's Fork, Brown Drakes can overlap with the slightly smaller Green and Gray Drakes, but large size is one of only a few characteristics they share with the other two mayflies.

June 25 is a typical target date for the Henry's Fork, and the emergence usually lasts through the first week of July. On Silver Creek–about 200 miles west and 1,000 feet lower in elevation–Brown Drakes generally appear two to four weeks earlier.

Brown Drake nymphs thrive best in relatively cold water where the stream bottom consists of sand and fine gravel. While silt is not a preferred habitat, I have heard reports of hatches on the Yellowstone, Firehole, and the headwaters of the Madison. Though I have not personally encountered Brown Drakes on those rivers, the mayflies have provided amazing fishing on some of the silted stretches of the Harriman Ranch.

The slender light brown shape of burrowing Brown Drake nymphs contrasts starkly with the dark portly form of a Western Green Drake nymph, and they are much more active swimmers. A preference for slow-moving and often shallow water could create a problem for anglers attempting to fish a size 10 imitation were it not for the Brown Drake nymph's mobility just prior to emergence.

A twitched retrieve of modest speed duplicates the behavior of a Brown Drake nymph as it nears the end of its underwater phase. But beware of the perils of a tight line when a strike occurs. Big flies attract big trout, and the take can be devastating to a 4X tippet, which is about as heavy as clear water allows. Surprise is the enemy when fishing a nymph imitation, and you must concentrate completely to avoid a break-off.

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Most of what I have read on the subject indicates dusk or shortly thereafter as prime time for Brown Drake emergence, and in my experience this is mostly correct. Spinners that hatched the previous day appear in the air at streamside when conditions are right for a Brown Drake emergence. The big mayflies prefer calm and relatively warm conditions for both the spinner fall and emergence, and both seem to have a disdain for bright days.

Spinners can begin to appear on the water as much as an hour before the first Brown Drake dun is observed. And spinners can be easily missed in their spent condition with wings outstretched—especially when the light is poor. This is important to remember because it is not rare for Brown Drake spinners and freshly hatched duns to be simultaneously available.

Fly Selection

It is a common assumption that large insects reduce the complication of fly pattern selection, and to some extent this is true. However, this applies mainly to smaller fish that have yet to learn the advantage of minimizing exertion in food collection, or do not require a large volume of insects to satisfy their nutritional needs. Neither has the painful experience of mistaking an artificial for a real insect taught them to resist an inaccurate imitation. Big trout in many waters have been caught and released numerous times and are conditioned to be skeptical of a faulty food form.

I learned many years ago that it is a mistake to assume what works for one individual fish automatically works for another. This is especially true during an emergence when the location of a trout determines the level at which its attention will be focused when feeding.

Trout in deeper water may find it more efficient to concentrate on subsurface foods when they are available during a hatch. Fishing a nymph at this time makes sense because it can be placed lower in the water column where a trout exerts minimal effort to capture submerged prey.

In shallower water, a nymph pattern may also be a productive choice because the movement that signals life often attracts trout. Such movement is characteristic of a Brown Drake nymph as it swims to the surface to emerge.

Emerging patterns are used to imitate a variety of images that result as the mayfly progresses from nymph to fully emerged dun. And while the individual configurations are generally fleeting, older trout seem able to identify a distinct form as being most attractive in terms of the ease with which it can be captured.

A good Brown Drake emerger fished in or beneath the film generally outproduces a fully emerged dun pattern because it represents something that is not about to fly away.

Most effective emergers are low-floaters that can be difficult to follow on the water—especially in poor light, which is the usual condition during a Brown Drake hatch. But while far from ideal with regard to comfort, this is frequently the only way to fool an exceptional trout.

By alternating between the CDC Captive Dun, the CDC PhD Emerger, and higher floating CDC Biot Emerger, I can usually find something that fits when emerging Brown Drakes are the target.

A high-wing dun pattern can be useful when Brown Drakes are sparse—which is usually early or late in the hatch. Trout holding close to the bank or away from the main areas of emergence can also be susceptible to a CDC Biot Thorax or Parachute. A slender body and sparse hackle are key features that elevate these patterns over something more bulky.

Brown Drakes are not exempt from a hazardous fate that can befall most mayfly species. The term "cripple" describes a mayfly that fails to fully separate from the nymphal shuck, leaving it helpless on the water and unable to fly to safety. Such vulnerability can make a Brown Drake cripple preferable to a healthy dun in the eye of a trout, and a pattern that floats fairly high can be an effective imitation. A CDC Parachute Cripple is remarkably accurate in duplicating the helpless mayfly and is also a real asset in visibility when the sun has left the water.

A lower-floating CDC Biot Cripple may be my favorite Brown Drake pattern because of its versatility and a track record that includes some very memorable trout. Tied on a heavier hook than usual, this pattern can be floated in the film when a trout dictates this type of presentation. This may require a few extra false casts and a gentle delivery to perform correctly. But this is a minor inconvenience because when the need arises, this fly can easily be pulled beneath the surface and twitched in a manner that simulates a swimming nymph in both behavior and general appearance.

The ability to instantly shift to a subsurface presentation can pay big dividends when trout are cruising in broad, slow, and relatively shallow water. Opportunity can be fleeting when a trout is on the move and a fly change is out of the question when the target may swim out of range in less than a minute.

A swirling disturbance is an indicator of nymphing activity, which differs considerably from the smooth and clearly defined riseform of a large trout feeding on the surface. In this situation, I usually lead the nymphing trout by about ten feet and begin a rather slow, pulsing retrieve administered with the rod tip.

Experienced fly fishers understand that selectivity to a certain phase of these oversize mayflies can be just as pronounced as when trout are feeding on the smaller varieties. In fact, Brown Drakes can be even more complex in terms of matching the correct pattern to the preference of an individual trout because all stages of the insect can be available at once.

Large trout in particular seem inclined to lock exclusively into a single form despite the presence of other choices. This behavior is probably based on superior availability when compared to a different stage of the insect.

It is a common mistake to be distracted by high-floating duns that rise nearly a half inch above the surface, and overlook Brown Drake spinners lying flush and motionless. Because Brown Drake spinners can outnumber duns by as many as ten to one, a spent pattern is often more productive. The key when fishing Brown Drakes is to be observant and prepared to fish any stage of the cycle as well as the interim emerging phases.

Sunset Hatch

Fishing Brown Drakes beyond sunset can often involve casting to the sound rather than the sight of a rising trout, and a hook-up can largely be luck when the fly cannot be clearly seen. However, the eyes will usually adjust to darkened water, and the presence of a moon or starlit summer sky can add visibility in the late evening.

Trout typically find a diminished volume of insects beyond about 10 P.M. and rigid selectivity seems to become more relaxed. For fishing at night, reliable flotation is my foremost concern in fly selection. Opportunistic feeding to remnant duns or spinners can often be addressed with a single fly that floats relatively high yet bears reasonable characteristics of both stages when darkness impedes the trout's ability to detect a fraud. Hackled patterns with Hungarian partridge or CDC wings are superb floaters that can be seen far beyond the time when a more sparsely dressed fly becomes invisible on the water.

Generally speaking, the timing of a Brown Drake emergence is about as predictable as any mayfly I know of. And while finding the big spinners on the water in early morning is not a unique occurrence, it is much more common to see the winged stages of Brown Drakes during the final hours of daylight and slightly beyond.

Most aquatic insects seem to obey no hard rule in the timing of their appearance, and Brown Drakes are no exception. This point was never more forcefully driven home than on a day in early July of 2010. Bonnie and I were joined by our grandson Zach on a warm morning below a large spring that feeds the Henry's Fork on the lower end of the Harriman Ranch.

Separated by more than 100 yards, we were each treated to an assortment of mayfly spinners and caddis that typify the most abundant time of the season. Seldom known for their charity, the big rainbows seemed unusually receptive to a PMD or Flav spinner for nearly two hours before their attention switched to a small brown caddis.

A lull in the action slightly past noon was perfectly timed for a leisurely lunch, and we assumed we would move to different water shortly thereafter. With the sun at its highest point, and the hottest portion of the day directly ahead, the likelihood of significant opportunity before early evening was remote.

A nice rainbow was nymphing in shallow water off the edge of a gravel bar where the river bends sharply to the left. Working from downstream, Zach was able to fool the 18-inch fish with a cased caddis larva.

An urgent disturbance at midstream diverted our attention as Zach released his prize, and a rise slightly upstream that followed was not subtle. At nearly 2 P.M., it became apparent that something very unusual was taking place.

Within minutes, the tall wings of large mayflies appeared over deeper water where the surface activity began to intensify. And in conditions completely contrary to what could be expected, we were soon engaged with a full-blown Brown Drake hatch.

For more than two hours we enjoyed the kind of fishing normally reserved for much cooler temperatures and darkened skies. And to make the day even more remarkable, the same spectacle was repeated four hours later and less than a mile downstream. While Brown Drakes cannot be expected to deliver more than eight hours of spectacular fishing during a single day, there is no mayfly hatch that does a better job of bringing big trout to the surface.

The image of giant mayflies backlit by a broad Western sunset is a sight that can never be forgotten. And when the audible rise of trout that may not be interested in surface feeding at any other time is added to the picture, you begin to understand the special summer event that Brown Drakes have come to represent.

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Rene Harrop is the author of Learning from the Water (Stackpole Books, 2010), and runs his own fly-tying operation, House of Harrop, from his home on the banks of the Henry's Fork.