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Fly Fisherman Throwback: A Primer of Stream Entomology–VII

A fly-fishing legend's seven-part series on bugs. Part VII: Riffle Areas–Feed Center of a Trout Stream.

Fly Fisherman Throwback: A Primer of Stream Entomology–VII

Riffles produce on West Branch of New York's Ausable. (Photo courtesy of New York Department of Commerce). Editor's Note: Image was colorized in Photoshop and may not be factually accurate. 

Editor's note: Flyfisherman.com will periodically be posting articles written and published before the Internet, from the Fly Fisherman magazine print archives. The wit and wisdom from legendary fly-fishing writers like Ernest Schwiebert, Gary LaFontaine, Lefty Kreh, Robert Traver, Dave Whitlock, Al Caucci & Bob Nastasi, Vince Marinaro, Doug Swisher & Carl Richards, Nick Lyons, and many more deserve a second life. These articles are reprinted here exactly as published in their day and may contain information, philosophies, or language that reveals a different time and age. This should be used for historical purposes only.

This article originally appeared in the April-May 1973 issue of Fly Fisherman magazine. Click here for a PDF of the print version of "A Primer of Stream Entomology-VII."


A river strange to a man is a flow of minor peculiarities. The twists and curls of the current that can buffet a fly or hide a trout are unseen after a cursory glance. The stream is a multitude of secrets, and it is not for the visiting or traveling fly fisherman to know all of the subtle truths immediately. But any sense of initial strangeness, in which a water can be blank to the reading eyes, is worth enduring to cast on a river such as the Pere Marquette of Michigan.

We sat in Howard Bresson's den, settled into soft chairs, sipping red wine from crystal goblets. I asked many questions to prepare myself to fish the river, and Howard answered with his reminiscences of the previous year, relating experiences of his first full season living near the Pere Marquette. "It's a fascinating stream," he finished. "Usually, I can't tell what the trout really want."

"Who can?" I asked. "Anyway, I need an excuse for carrying so many patterns."

In my circular fly box were the rough water dry flies, the flies that I use on the riffle stretches of the western rivers, big flies such as the Caddis Buck, Humpy, and Picket Pin. Howard fingered through the sections of Wulff and Trude patterns, holding up a No. 8 Royal Trude, "Is this one any good in Montana?"

I picked up the downwing fly, nodding, "Sure, it's great on fast water, where the problem is visibility. The fisherman needs something bright to see among all the foam. The trout needs something big to see among all the bubbles."

Howard assured, "There will be bubbling water like that tomorrow."

''I'll see if I can't catch a fish on that fly."

"I think that you may have to work for it," Howard said.

After the drive to the Pere Marquette in the morning I stopped to study the river before beginning to cast. The current cut and dug deep into the loose sections of the bottom strata, leaving fish-holding bends and pools. I waded slowly in the deceptive tugs of the flow, watching for movements of feeding trout, screening the gravel of the riffles for samples of nymphs and larvae, peering close to the surface for signs of insect activity.

Howard caught his third brown of the first hour, a well-formed 13-inch fish indicative of the good bottom production of the river. He came across the spit of current to join me, "Do you have the river figured out yet?"

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A fly angler checking behind himself for his backcast on a forested rocky stream.
Trout don't like to work harder than they have to, and usually lie at edges of heavy runs. (C. Boyd Pfeiffer photo). Editor's Note: Image was colorized in Photoshop and may not be factually accurate.

"No, but I can't hold off the urge to fish any longer, and what I don't know now, I can only learn by fishing the water."

Howard clambered up onto the bank to take a break. "Usually," he called to me, "the fishing slows down now. This is really an early-morning and late­evening river for dry flies."

"You're just what I need, Howard, a prophet of doom."

"I'll just watch, old buddy."

An upstream riffle twisted through the shade of dangling tree limbs. I cast the Royal Trude to the far edge of the faster sluice, spotting it within inches of the shore line. After many casts traveling the same drift lane I saw the flashing arc of the trout rising, and I hesitated before I set the hook. The trout, a brown, acted like a rainbow and tail­slapped twice. He moved up through the riffle and fought near the bottom of the adjacent slick. I kept enough side-pull pressure to tip his balance in the current, and as the flow of the river tired him, he surfaced for a final splashing flurry. Howard stood in the shallows with the net and I led the fish into us, where we weighed, measured, and released the 18-inch trout.

I pointed out to Howard, "Who can tell what the trout want?"

What might have been a fine day proceeded to become a great day. The angling that followed was the rare flush of propitious luck, where each serious strike was hooked, and each hooked fish was cleanly landed. Howard stopped watching and asked, "Can I borrow one of those Montana flies?"

I handed him a #8 Red Trude, the original prototype of the pattern, "For that matter, it's an Idaho fly."

"Idaho?"

'The Trude was first tied in Idaho by A. S. Trude in 1901. It caught over a hundred trout on the first day that it was tested."

Later, as I landed the second 16-inch rainbow of the day, Howard added, "You know, you might end up catching a hundred fish today yourself if you don't watch out."

In the bright sunlight of mid-day I concentrated on the bouncing water, where the refracted light and trapped air rode a protecting roof over the trout that stayed in the riffles to gather the drifting caddis larvae or floating terrestrials. In the riffles, where the trout found protective cover, available food, and aerated water, rainbows and browns fed throughout the day. The fish slashed at the unraveling Royal Trude.

Like a heavy terrestrial, the Trude sat flush in the surface film, greased and dried by false casting just enough to fish damp in the water, rather than dry. Aiming so that the fly landed indelicately with a splat, I put my casts to the edge areas of the riffles. The trout were lying at the borders of the heavy runs, close among the bottom rocks where the current force was minimal.

The silhouette of a fly angler removing a hook from a trout in a river.
(Russell Tinsley photo). Editor's Note: Image was colorized in Photoshop and may not be factually accurate.

We quit fishing late in the afternoon, taking time to rest and eat supper before returning to the river to see if an evening flurry developed. During the day I stumbled onto many more trout than I deserved to see, and now Howard remarked, "You fished it like you owned it."

As we walked to the truck I said, "Oh, I guess that trout are alike everywhere." But I pondered on experiences that were not so predictable, and added, "Only sometimes they're more alike than at other times."

On the Pere Marquette the trout were in the faster water, alert for drifting food. With the scope of vision of a trout extending forward in a 300° arc, both underwater and surface objects were visible as they approached a lie. It was possible, with a number of casts to an area, to trigger a response to the flush Trude. Each likely area deserved a number of drifts, since the fish were present with intent in the riffles.

In many streams with rocks large enough to form sheltering pockets, the riffles are the feed centers for actively foraging trout. In the typical freestone stream over 80% of the insect production is generated in the flowing, shallow areas. Midge larvae, most species of stonefly nymphs, clinging and clambering mayfly nymphs, and filter-feeding and free-crawling caddis larvae all inhabit the gaps under and among the bottom stones. On the surface of the flow any blow-in terrestrials or emerging mayfly duns are funneled into the dominant drift lanes. The feeding trout can wait at the edge of the current to pick at all of this passing fare.

The fast-water fish exists as an opportunist. Usually, the feeding in the bustling environment of the riffles is not ultra-selective, but if a large number of a single kind of insect appears on the surface the trout may fuss over the size and silhouette of a matching pattern. An emergence of mayflies, a fall of grasshoppers, or an egg-laying dive of stoneflies may make even unsophisticated trout establish a feeding preference.

Last summer, with the informal schooling of Dr. Harold Habein and his boys, Peter, Jared, and Chris, in the intricacies of fly fishing, we witnessed a spurt of selectivity in wilderness cutthroat trout. The previous evening, as I regaled the doctor with the glory of fussy angling over wary fish, I ended with the qualification, "But we probably won't have to worry about matching the hatch here."

When we camped for a lay-over day during our raft trip down the South Fork of the Flathead River, our group hiked the short trail up the Big Salmon River. I picked mayfly duns off the streamside foliage and showed them to Dick Fryhover and Doc Habein. "But the fly won't make a big difference to the fish," I said.

"What would you use to match it?" the doctor asked.

I looked through my boxes of patterns. I took out a #14 Beaverkill Red Fox and held it up against the blue­grey living insect. "This one is close."

We prepared to fish when we reached the river head, at the outlet of the lake. Since the Red Fox nestled in my hand, I tied it onto the leader tippet. The jaunty little Fox rode among the rocks and washes, swirling to the pocket water. The hatch of mayflies grew heavier as the morning warmed, rushes of duns popping from the bounces of the river. The first six casts with the Red Fox caught cutthroat. "But any fly would work now," I added.

I waded downstream, putting the fly into creases and pot holes. The abundant trout of the river rose for the mayflies, and took the Red Fox at every rock. Each bright fish dashed recklessly at the fly, flashing a warning of silver if the sun-rays reflected from its turned side, splashing clumsily when it felt the pull of _the hook. I beached and released the I 0- to- I 4-inch cutthroats, the fish blending in the clear water to the yellow of the gravel as they swarm away.

The mayfly emergence continued undiminished, but as I sat on the bank for a noontime break I saw the first of the large yellow stoneflies. The lumbering insect flew a preparatory flight over the water, circling high, and then it dove low to skitter onto the river. More of the insects appeared in the air. I splashed through the riffles, attempting to grab a specimen, finally lifting one from the water before a trout devoured the floundering stonefly.

The specimen cupped in my hands was the common western species, Acroneuria pacifica, known to area anglers as the willow fly, but the insect that I held was both larger and lighter in color than samples of the same species that I collected earlier in the year from the lower-altitude rivers of Montana. The insect was a straw yellow in color and the match of a #6 hook in size, whereas Clark's Fork or Rock Creek specimens were light brown and the match of a #8 hook.

As I resumed angling with the Red Fox still on my tippet, since the mayfly hatch remained heavy, I waded back upstream to rejoin the group. My attention was not so much on my casting as on the increasing number of willow flies in the air and on the water, and on the feeding frenzy of the trout leaping and slashing for the insects. Without noticing the slack off in the rate that I was catching trout, I continued casting until the little Red Fox was not catching any trout at all.

I thought possibly the lack of strikes was due to inattention to the details of casting. I concentrated, placing the fly over the lanes of active trout, but definitely now the Red Fox was minus the previous magic. In the rough riffle water of a wilderness river teeming with avidly feeding cutthroat trout, a fly matching the numerically dominant insect on the water was not catching fish.

I moved up to the river head, and met Jared and Dr. Habein beside the stream. They were also watching the growing orgy caused by the suicide crashes of the stoneflies. Jared pointed out a scoop of deeper, quieter water against the far bank, "We saw a nice fish jump there."

Cover of the April-May 1973 issue of Fly Fisherman magazine featuring a fly angler seen through a gap in some leaves.
This article originally appeared in the April-May 1973 issue of Fly Fisherman.

We watched the half-moon patch of water, and we calculated that two trout were feeding, one high and one low on the line of drift, each cruising for the stoneflies that curled into the area from the current. Doctor Habein suggested, "Try them."

"I bet they won't take the Red Fox," I said.

I waded into position, casting hard above and beyond the distant shore, snubbing the line to pull coils of slack onto the faster intervening current. The fly dallied prettily on the slow pace of the pocket. The trout pursued the erratic stoneflies and fifteen casts with the Fox were unsuccessful.

I picked out a #6 Sofa Pillow. I urged the doctor to try for the trout, but he insisted that I deserved the first chance. The fly pattern was darker than the willow flies, but the hair wing lay flat along the back and outlined the proper silhouette. The point on selectivity was mine to prove, and the trout were cooperating when they refused the little Red Fox.

I measured the distance with false casts and popped the fly back towards me with the checked line. Twice the fly landed well enough, gliding freely among the trout, but the splashing, flailing struggle of live insects attracted a striking flurry. The third cast landed alone in a gaggle of falling stoneflies, and the cutthroat at the bottom end of the flow gobbled the fake. I bulled him into the fast water, leaving the second feeding trout undisturbed. I tired and landed the 15½-inch fish.

I handed the rod to 14-year-old Jared, and explained the mechanics of the required cast. He waded into the riffle, a boy who had never used a fly rod before the trip began but who now was a veteran of over seventy trout. He put the fly across, and on the fifth cast he hooked the second cutthroat, playing him with the practiced hand. He released the fish, a twin of the first.

The shadows of late afternoon were growing to block the sun from the river, and we started back to the camp for a hot supper. We followed the path, tarrying to pick huckleberries from the hillside, musing upon the vagaries of trout in general. I explained to the doctor and Jared about these cutthroat that were not supposed to feed selectively. "You know, the only ones who are never really wrong about what they want are the trout themselves."

We turned with the trail away from the river and left the trout and the stoneflies to their necessary ritual.




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