The Pale Morning Dun

by Mike Lawson

The Pale Morning Dun is probably the most important mayfly hatch in the western United States. You'll find them from the soft currents of Fall River in California to the bouncing riffles and runs of the Madison in Montana; from the wide expanses of the Henry's Fork in Idaho to the secret side channels of the Bow River in Canada; and from the gentle glides of the Frying Pan in Colorado to the great runs of the Green in Utah. Find a good trout stream in the west and your odds are almost 100% that it sports a good hatch of Pale Morning Duns.

Their vast distribution is not the only factor that makes these light olive-yellow mayflies so important. The peak of the Pale Morning Dun hatch occurs during the middle of the summer while most trout water in other parts of the continent is sleeping through the hot dog days, waiting for the cool autumn nights to give new life to their treasures.
Pale Morning Duns were among the first mayflies to kindle the interest of early angling entomologists.

They belong to a large family of mayflies known as Ephemerella and three species: infrequens, inermis and lacustris were first identified as being important to the trout fisher. Later studies indicated all three of these species may not be equally important. Identification of exact species is so difficult that some confusion still exists among the scientific fraternity so it is very doubtful that the trout we fish for knows or cares what species he's feeding on.

My own research indicates that the species of inermis far outdistances the other species in angling importance. The most important point to realize is that all three species are virtually indistinguishable to the eyes of the trout fisher and more importantly, to the trout.

My first experience with these magnificent little insects goes way back before I even realized what a mayfly was. I spent many a bright summer day fishing the soft, weed-lined flats of the upper Teton River near my home in Idaho and watched the big Cutthroats feed softly on the tiny yellow mayflies. I hated them because once they appeared on the surface, the big fish quickly lost interest in my wet fly offerings. I was rewarded with a token fish on rare occasions using a Light Cahill with a lucky cast after the dreaded yellow flies appeared. I didn't know what they were but I knew the trout loved them.

I found out what the light yellow insects were when I received a copy of the now classic book, Selective Trout by Doug Swisher and Carl Richards. I was amazed to read about water in my very back yard, the Henry's Fork of the Snake. I read all I could about the little mayflies I had grown to know so well, the Pale Morning Duns. Later I had the privilege of accompanying Rene' Harrop to Nelson's Spring Creek and fish with Doug Swisher. We fished hard all day and tied flies all night. I learned more about Pale Morning Duns in those four days of fishing that wonderful spring creek than I could in a life time of ignorantly bumbling along on my own.

Since those apprentice days I have fished magnificent hatches of Pale Morning Duns on the great trout streams of the west. A good morning hatch of them once saved an otherwise loser of a day for me on the Beaverhead near Dillon. Memorial Day often found me on the Firehole River looking for those first hatches of the yellow mayflies. I still eagerly anticipate each opening day of fishing on the Henry's Fork to meet the first hatches of the Pale Morning Duns.

Although most western trout streams support good populations of Pale Morning Duns, the greatest concentrations occur in streams with medium velocity currents. The nymphs are sprawlers and thrive on rocky or gravel bottoms interspersed with good stands of aquatic vegetation. On some streams their population densities are astounding, with hundreds of nymphs per square foot of stream bottom. The nymphs are robust and vary greatly in coloration from a pale yellow-olive to a deep olive-brown.

Pale Morning Duns are medium sized mayflies. Their body size ranges from 6 mm to 9 mm in length which corresponds with size 14 to size 18 hooks. Like several other mayfly species, they get smaller as the season progresses. This phenomena was first pointed out to me by Fred Arbona while doing research on his great book, Mayflies, the Angler, and the Trout. Early in the season the Pale Morning Duns will be best matched with size 14 and 16 hooks.

Later on, in August, the same species will be at least a full size smaller and are matched with size 16 or 18 hooks. This factor might account for the confusion in identification of species by early angling entomologists. Another consideration which can lead to confusion is the differences in body coloration of the duns. The females run a pale yellow olive to pale chartreuse while the males often have a pronounced rusty appearance. The wings are light to medium grey and often show a distinct yellow on the leading edge, especially on the females.

Emergence is greatly influenced by a variety of conditions including water temperature, humidity, and light intensity. Because Pale Morning Dun hatches occur over a prolonged period of several weeks on most trout streams, the emergence of duns and spinner falls often vary in intensity and time of day, according to the influencing conditions. Since the hatches continue through the warmer months of the season, the best activity usually occurs on cool, humid, overcast days. Unlike many mayfly species, each stage of the life-cycle of Ephemerella inermis is of considerable value to the fly fisher. To be successful, anglers should become familiar with each stage and how to learn capitalize on each fishing opportunity.

Nymphs

I've had my best nymph fishing during and just prior to the hatch. The nymphs generate a lot of energy just before they emerge and wiggle and twist as they ascend toward the surface. The trout waste no time in taking advantage of this opportunity. In spite of the activity, nymph fishing during these conditions can be frustrating and unsuccessful. Since the nymphs are bouyed to the surface as their body processes change, they drift down the feeding lanes where the trout hold to intercept them. Any unnatural drift will be ignored by all but the smaller fish. Fishing a small nymph with a drag-free drift can be much more difficult than fishing a dry fly on the surface. For that reason, blind casting the nymph randomly among the feeding fish is usually met with a low degree of success.

Whenever possible, I like to cast my nymph imitation to a visible, sighted trout. Of course this is not possible under many conditions, but on clear, spring creek waters, it can be a very effective method. After you spot the fish you must determine the drift lane from which he's picking his food. Cast the nymph a few feet above the fish and allow it to drift naturally through his feeding lane. You might need to grease most of your leader to keep the fly from sinking all the way to the bottom. Usually you won't feel anything or even see a slight twitch in the line or leader. You must have a "feel" for where your pattern is and look for the tell tale white mouth as the fish opens to intercept your offering. Often the fish will just turn his head slightly as he takes the fly. This can be one of the most exciting experiences in all of fly fishing.

Since many situations won't allow you to actually see the fish, an alternative method is to use a strike indicator. There are many types of indicators available and all will work wonders if they're fished correctly. Some of my own favorites are small, one inch plastic sleeves, the pinch-on foam indicators, or a small piece of bright yarn tied with a clinch knot to the leader. I like to position the indicator according to the depth of the water I'm fishing, which is usually 2 to 4 feet above the fly. Although indicators are designed to help the angler determine the soft take, I find them even more valuable for maintaining a natural drift on the fly. Watching the indicator will give you a better idea of how the nymph is performing under the surface and allow you to mend and manipulate the line to correct the drift.

Several years ago I was fishing a favorite stretch of the Madison River. The Pale Morning Duns were starting to hatch when I arrived but I saw few fish rising. I decided to try a nymph and knotted a size 16 Pheasant Tail Nymph to my 5X tippet. I found a nice pocket where the current flowed between two large rocks and fed into a long slick below. I knew there had to be some good fish working on the emerging nymphs in the margin between the fast water and the slick. I expected a strike on every cast but my enthusiasm soon waned after dozens of fruitless casts. I sat down on the bank and considered changing flies. I noticed some bright orange yarn in my vest so I clipped a small section off and tied it to my leader with a clinch knot about 3 feet above the fly. I waded back out and took up my same position. The first cast saw the indicator go slicing through the current with unnatural drag. I knew as the indicator went, so went the nymph. I found my position impossible to accomplish a drag-free drift with the nymph.

 I found a better angle and this time I watched the indicator drift down the slot in a natural, drag-free drift. The next cast the indicator hesitated and I tightened the line and was fast to a racing, high jumping rainbow. I took several nice trout from the run and was equally successful at each of the next spots I stopped to fish. The indicator not only helped me detect the subtle takes but it also pointed out the tell tale imperfections of the the drift which would surely lead to refusals.

I believe the presentation is much more critical than pattern when fishing the nymphs of the Pale Morning Dun. Usually a size 16 or 18 Pheasant Tail Nymph will do the job. On occasion I've found a pale olive nymph tied with natural fur and ostrich herl to be highly successful on selective trout, especially on the clear Montana spring creeks.

Duns

I've experienced my most frustrating moments fishing to the selective rainbows of the Henry's Fork during a mid-summer hatch of Pale Morning Duns. The hatches are influenced by such a wide variety of climatic conditions that the anglers must be prepared with a wide range of dry fly patterns. The variety of the water fished will also have a great influence on the most effective imitations.

Early in the season, the duns usually start emerging in mid-morning, around 10 or 11 o'clock. As the season progresses and the days get warmer, the duns will begin earlier and last only a short time and then begin again in late afternoon. On cloudy days the hatch can quickly become full-blown and literally carpet the water. During prolonged dry weather the duns will hatch sporadically throughout the day.

The type of water fished will dictate the requirements for the most effective imitation of the dun. Since good hatches of Pale Morning Duns occur on all types of water including fast, medium and slow currents, the angler should be prepared with fly patterns which are best suited to the stream configuration. It's hard to beat a delicate No-hackle for the soft flowing, weed lined glides of a majestic spring creek. The same No-hackle would quickly be dashed under the surface of a brawling, fast flowing river like the Gallatin. For fast flowing streams where visibility and floatability are paramount, I like a fully hackled standard pattern to imitate the dun. Another important pattern to help fill in the gap is a thorax or parachute.

Unfortunately, the correct fly pattern tied to represent the fully hatched dun at the peak of emergence is no guarantee of success. Pale Morning Duns drift a considerable distance after they break free from the nymph shuck before they raise their wings to the upright position. I've witnessed the duns sitting in the surface of my aquarium for several minutes before they get their wings up to become airborne.

During cool weather, the trout will selectively feed on these emergers with their wings folded in the down position. You must be prepared with a variety of emerger patterns to be successful in this situation. One of the best emerger patterns is the floating nymph. The clump of dubbing which forms the wing case represents the folded wing and provides visibility. This fly should be dressed and fished flush in the surface film.

Another effective pattern is the soft hackle emerger which incorporates a soft hackle, wound wet fly style at the front of the fly. Although this fly works great on flat water, it's equally effective on broken water. It can be dressed and fished in the surface film like a floating nymph or fished wet, just under the surface.

My third emerger choice is the Quill Wing Emerger designed by Rene' Harrop. This pattern is tied with short, duck quill wings and is a killing pattern when the selective trout are tuned into the slow developing duns.

Because many Pale Morning Dun hatches occur on warm, dry afternoons, the mortality rate is high and many insects die before they escape the surface of the stream. They dehydrate quickly and many of them don't escape the surface to reach the safety of shade and shelter. I've never seen more selective trout than those which feed on the hapless duns which did not survive the ordeal of emergence on a warm, dry afternoon. These trout will ignore each natural dun that drifts over them and continue to rise to these cripples and drowned duns which seem to appear invisible to the angler. These rise forms are usually very subtle, slow and deliberate.

Several patterns to represent the dead and dying duns have proven effective for me. Harrop's Captive Dun represents the dun which didn't get it's wings unfolded. It trails a maribou tail to represent the nymph shuck still attached. It should be fished flush in the surface film. Another great pattern is the Drowned Dun which is tied with duck quill wings, like the No-hackle, but the wings are tied in the spent position. It also has a trailing nymph shuck represented by sparse strands of yarn. I often cut one of the wings off on the stream as many drowned duns drift down tipped over on one side. Even with the correct pattern, the fishing can be very difficult. Since the productive patterns are designed to drift flush in the film, they are impossible to see. In addition, you have to carefully time the casts to coincide with the gentle rises of a lazy trout who has all day to feed at his leisure.

Spinners

The spinner fall of the Pale Morning Dun is as important to the western fly fisher as the the hatch itself. Mating flights usually occur both mornings and evenings. Early in the season, in June and early July, I've had my most productive fishing to the spinner falls during the late evenings. I've often failed to notice the change from the greedy rises of a caddis emergence to the soft, gentle rise forms of the spinner fall during the last moments of daylight. Later on in the season, especially during August when the days shorten and the evenings are cool, I find the best spinner falls occur during the morning hours.

The spinners usually mate, lay their eggs and die, the day after they hatch. They can hit the water in unbelievable numbers, with several hundred crumpled bodies per square foot of surface area. I make a special effort to be on the water, armed with spinner imitations, the first bright, clear morning after a day of cool, cloudy weather. As I've previously mentioned, the duns hatch in good concentrations on cloudy days and the potential for a great spinner fall is excellent after a good, cloudy day followed by a bright, warm day.

The spinners like to drop their eggs where the current speeds up. You'll find some of the best fishing in and just downstream of riffled areas. The bigger trout will take up the prime feeding locations in the margins of the riffles, in the pockets and slicks, and in front of large rocks. With good numbers of insects, the largest fish will quickly develop an intense feeding rhythm, rising several times in succession and then holding for a few moments before rising again. In addition, they often cruise back and forth across the feeding lanes gulping the spinners by the mouthful.

Coupled with low light conditions, this situation can be one of the most challenging projects in all of fly fishing. I've stood in the Henry's Fork many an evening, with other anglers all over and the river covered with hundreds of rising fish feeding on spinners, and not seen a rod bend or heard a reel sing. Precision casting is essential and timing the rise is of the upmost importance. You'll find you can wade quite close to trout which are greedily stuffing themselves on Pale Morning Spinners. You should take advantage of this and work close enough to a feeding fish to get as many drifts as possible without false casting. It may take several hundred casts before the trout selects your pattern among the hundreds of naturals, and you don't want to waste casts by false casting.

Short casts will also greatly increase your accuracy and give you a much better idea as to where your fly is. Since spinners are virtually impossible to see, you just tighten the line each time you see a rise that's in the neighborhood of where your fly ought to be. Most of the time you'll come up empty but even a blind hog occasionally finds an acorn and it's hard to describe the excitement you'll feel that one time when you tighten and the resistance is there.

Pale Morning Spinners come in two colors and you'll find both varieties on the water at the same time. The females retain essentially the same pale yellow coloration they have as duns while the males turn a rusty brown. Since virtually all of the females will end up on the water sooner or later to lay their eggs, you'll need some patterns with pale yellow bodies. You'll also need some rusty spinners to match the males. While I'm not saying that the trout always show a preference for color, I do think its wise to have patterns in both colors. I've usually found a pale yellow spinner to be more productive on bright, clear mornings. In the low light of dusk, a rusty spinner will often out produce a yellow one because the dark body offers a better silhouette against a grey sky.

My favorite pattern is the simple hen spinner first originated by Doug Swisher and Carl Richards. I tie the wings in the spent position so the fly will drift flush in the surface film. Since the wings of the natural are clear, I like to use medium grey hen hackle tips to blend with the sky. I believe wings that are too light in color show too much contrast to a trout which is viewing the fly against a bright, blue sky. Sometimes I wind a dun hackle through the wings and clip it on the bottom to add a little visibility.

While other larger insects like the salmonflies or the green drakes have become legends to the western angler, their hatches are often unpredictable. It's easy to become so enchanted with dreams of huge trout fighting each other to feed on the huge insects that can't see the forest for the trees. The Pale Morning Duns are the real heros of the west, even if they don't get the recognition they deserve.

Not long ago as I arrived at the river, I saw the Pale Morning Duns were already on the water and the fish were starting to rise. I soon spotted the familiar tell tale rise of a large trout and I worked into casting position. As I watched the big fish feed, my mind drifted back to this same spot nearly two decades ago. I worked for the forest service in those years and each afternoon found me riding my dirt bike through the dust filled ruts of Wood Road #16 to this special spot. There was a huge rainbow who held just off the bank above an old car body that rested partially in the water. The trout was an old monarch who had nothing to fear from me. He had beaten me many times and repeatedly spurned my offerings as he fed on the pale yellow mayflies. This was another day however, and I had some fresh, new patterns that I had spent several hours slaving over at the vise.

They were No-hackle duns and compared to the flies I can tie now, they were crude to say the least. I had confidence in them and that's what counted the most. It was a perfect day and the meadows of the Harriman Ranch were white with the blossoming Mule's Ears. The snow on Mount Sawtelle provided a picturesque back drop as I walked down the hill to look for the big fish.

The big rainbow was in his usual position and I waded into my usual position. Experience had not yet taught me the tell tale rise of a large trout. Had I not spooked him out from the bank a few weeks earlier, I'd have never known the gentle dimple he left was the rise of a large fish. After I reached my spot I waited and the big fish rose. I felt my confidence level drop as I heard the sound he made as he fed. It usually only took three or four casts to put him down. I took a deep breath and made my cast. It looked good and the fly landed about two feet ahead of him and drifted downstream. His nose came out and he inhaled the fly. I couldn't believe it, he'd taken it on the very first cast! When I tightened the line it was solid, as if attached to a rock. For a moment I actually thought I had hooked the bottom because the fish didn't move.

Up to this point, everything was going according to plan. What happened next, didn't. When the big trout decided he was really hooked, he raced through the shallow water for the middle of the river ripping off coils of loose line. When the loose line hit the reel, he vaulted into the air and his broad, silver side appeared in slow motion as he augured back in with a big splash. Now he was on the reel and it protested loudly as the fish ran on. He went airborne again, this time in a series of long, greyhound jumps. It was too much for me and I could no longer resist the urge to apply pressure to try to slow him down. I pressed the line against the cork handle and it was over, the 5X tippet parted and the line was limp. I reeled in the loose line and muttered in disgust. I'd have killed the fish if I could have landed him. I could envision the envy my friends would experience when I showed them the big trout. My lack of understanding in those days made the result of my fishing more important than the experience. Today I'm glad I didn't land that fish because the picture of that big, silver slab against the clear mountain sky will last forever on my mind.

Since that day, there have been many other trout, some lost and some won. The old car body still rests against the bank at Wood Road #16 but it has now moved downstream nearly two hundred yards. The old trout has doubtless died of old age but his legacy lives on; the legacy of clear water, rising trout, and Pale Morning Duns.



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