Charles E. Brooks, retired US Air Force officer, an avid trout fisherman who loved to fish the rough and tumble rivers of Montana located in the Yellowstone area, had a two pronged problem to solve, namely to invent an imitation of the giant black stone fly nymphs that the rainbow trout would mistake for the real deal, and how to get it down between the big rocks embedded in the bottom of riffles and glides of his home streams using a fly rod.
The Pteronarcys nymphs, some as long as a man’s thumb, most the size of a woman’s, are bottom dwellers that graze atop and between the boulders that decorate stream beds. At times, they unhook themselves from the substrate and go with the flow. These dangerous drifts appear reckless at first, since they leave the bugs naked and vulnerable to trout that dart from their ambuscades like heat seeking missiles and pick them off. Scientists call this behaviour benthic drift, and have devoted a lot of research to it. There are many theories as to why aquatic benthos behave this way. Charlie Brooks pored over the papers published by entomologists with the practical eye of a trout fisher. To Charlie, how the nymphs drifted was more important than why they did.
He learned that most of these drifts occurred at night, which didn’t surprise him since a nocturnal float at least afforded the creatures the cover of low light. Brooks was pleased to discover that benthic drift occurred during the day too, but not as often, and usually on darker days. After a lot of field work, he learned to spot the conditions when benthic drift was happening in broad daylight. During these prime feeding times for trout, Brooks’ imitation needed to be fished near, but not on, the bottom. To this end, he loaded his reel with the fastest full sinking fly line of the time, which, by today’s standards, would be a slow sinking line. On the end of that line, he attached a short length of heavy monofilament, the heavy nylon being necessary to turn over a large heavy fly.
To imitate the stonefly nymphs, Brooks wound an underbody of lead wire on a long shanked streamer hook with a #4 gape. Next, he fastened a pair of small quills from the leading edge of the flight feather from a goose to the bend to ape the tails of the stone nymph. To create the segmented effect of the insect’s exoskeleton, he wound a body of black mohair, then spiralled some medium copper wire over it in even turns. Finally, Brooks took a pair of rooster hackles, one brown, the other grizzled, and wound them through the fake bug’s thorax, thus simulating legs and gills.
Out of water, Charlie Brooks’ Montana Stone nymph, didn’t look like much (go to stevenojai.tripod.com and scroll halfway down the screen to see an example), but once it was submersed, it bore an uncanny resemblance to the aquatic invertebrate it was meant to imitate. During his early experiments on the stream, Brooks learned that the fly patterns tied to mimic the yellow and orange undersides of the natural nymph actually spooked trout when they flipped upside down in the turbulence. Consequently, he constructed symmetrical nymphs that always appeared to be riding right side up in the flow whether they were or not.
Of course, coming up with an effective pattern was only half the battle. To best imitate the drifting nymph meant fishing it so that it was free of drag. Drag is fly fishing argot that refers to the pull of leader and line on the fly. Drag is the bane of dry fly fishers because insects floating atop the water float freely. Since a floating fly is attached to tow rope consisting of tippet, leader, and fly line, the latter is always trying to drag it across the top of the water like a minuscule water skier. Flies behaving this way fail to trip the hair trigger instincts of trout. As a result, the angler fishing dry flies is forever readjusting his line to keep his fly floating freely as long as possible. Brooks’s task was to achieve the same kind of extended free float underwater, a much more difficult feat.
To affect this, he cast a short line upstream just as a dry fly fisher would, retrieved line as the bug drifted toward him, while simultaneously lifting his 8 weight, 9 foot fibreglass rod as the nymph passed him. As the nymph continued its journey downstream, he lowered his rod and began paying out line. When the nymph began to drag, Brooks cast it back upstream with a crisp flick a little farther from the bank than the cast before. The whole technique is like deceptively difficult to do well but once mastered, very effective.
After reading Brooks’s Nymph Fishing for Larger Trout, I devoted a lot of fishing time to his nymphing technique. As Charlie predicted, I caught a lot of trout with it, but it was not until I met Hugh that I realized it had a much broader application.
Continued next week…