That modification came in the summer of my tenth year, as my father and I were fishing a deep, cliff-side pool on Wyoming’s Green River. I was casting a big Strip Leech on a floating line and catching nothing. My father, on the other hand, was doing a good impression of a fish-exercising machine. Eventually taking pity, my father forced me to switch to my sink-tip line, a shorter leader, and a couple of bulbous split shot. He told me to cast and mend just above the pool’s lip, to allow the fly and sink-tip to go deep, and to work the fly back with an active, but measured retrieve.
A few casts and retrieves later, something slammed the leech and made a charge for the tail of the pool. My father grabbed me and we gave chase, hoping that my tippet would hold. Just above the next set of rapids—where I would surely lose whatever was attached to my line—my father made a daring, diving scoop. And there it was: the page 156 brown in all of its glory. My angling life had been made (temporarily) complete, thanks to some behavior modification.
When it comes to behavior modification, there are a number of factors that can come into play, including the materials used in the fly itself. The famed Clouser Minnow is perhaps the best-known example of a fly that uses weight to great advantage. Little more than a hair-wing coupled with dumbbell eyes, Clousers go down now, and when retrieved with a rhythm they can create a fish-enticing jigging motion. The caveat with heavy flies such as Clousers is that they are just that: heavy. In areas of complex bottom structure, you need to keep the fly moving. If the bottom can be navigated safely, however, a heavy fly can sometimes be “walked” along—particularly in flowing waters—using a combination of well-timed rod lifts and the natural tumbling effect of the current. Joe Humphreys has a thorough description of this “walking” tactic in his 1981Trout Tactics book.
Conversely, flies that are built with little or no weight do not enjoy such deep-diving benefits. Careful line manipulation and/or smart use of currents, however, can work wonders. When fishing Russia’s Kola Peninsula a few years back, the most successful Atlantic salmon fly that I used was Mauri’s Magic Muddler, a thinly dressed, non-weighted, marabou-based design. The slight build of the fly really came into its own one day on the Aquarium Pool of the Sidorovka. I used the lee of a mid-stream boulder to position the fly line at mid-length, while the fly slid around in the main current, ultimately hovering a few inches under the surface in the eye of the pool. Although the fly only held position for a few seconds, it was enough time for a very acrobatic Atlantic to take notice. The light fly really helped to make the whole thing work.
Adding weight to the leader can further alter the dynamics of the system. I typically use split shot (or sometimes putty), and typically place the weight anywhere from the eye of the hook to a point about six to a foot in front of the hook. With putty it is possible to place the weight directly on the head of the fly (a bit of post-construction fly design).
Those who put in serious hours on lakes may want to take a weighting lesson or two from the stillwater anglers of the UK. One tactic is to combine a buoyant fly (foam-headed patterns are good choices) with a fast-sinking line. The line dives deep while the fly wants to go for the surface. A slow, pulsing retrieve makes the fly work like an anti-jig, crawling along above the bottom and rising during a pause.
Having a working knowledge of behavior modification is not the end-all to making your fly effective, but it can go a long way toward greater fly-fishing success—and perhaps a page-156 brown of your own.