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Lately, I’ve been thinking about why trout accept or reject a fly. Specifically, when a trout does eat the fly, was it looking for a certain drift or a single position?

Sometimes, a near-perfect dead drift of the dry fly or nymph is critical for success. These are times when trout need the fly coming down one lane, at the right speed and for a considerable distance. These trout need long, extended drifts to judge the presentation and finally commit.

But just as often, trout seem to smack the fly as soon as it enters their window — or their area of focus.

Imagine a trout hanging on the inside, back edge of a moderately paced seam that slides around an exposed boulder. Now imagine a Hendrickson hatch that is strong enough and lasts long enough so trout throughout the river are aware of the vulnerable duns and ready to capture them. The trout holding in our perfect boulder-seam might have a window of just six-inches, from where the current bumps into the rock to a half-foot downstream. And if the trout has its nose extra close to the origins of that seam —very near the boulder, then six inches is about all it gets, as the current slides around the rock. A trout in this position and in this mindset isn’t looking for a dead drift. It’s looking for a Hendrickson to enter that small window. And when it does, our trout intercepts the fly, (almost) regardless of the drift quality.

This trout is selective about the pattern, as it’s looking for Hendrickson duns, but it is not selective about the drift, simply because the window is so small. Our trout is looking for a fly in a position. It doesn’t have time or space to analyze the drift. So you might very well drag and slide the fly through this selective trout’s window and score the fish of the day.

To the counterpoint, another trout, laying fifty yards upstream in the exposed tailout, might show the opposite tendency — being very selective about the drift, but in a not-so-small window. This trout scans upstream in a wider field of view. Inhabiting softer currents, it’s willing to move left or right, perhaps even a few feet to make a meal of a number twelve Hendrickson dun. But because the trout has so much room and so much time to observe the fly approaching and cruising through its large window, this trout becomes extra selective about the quality of the drift. Try dragging your hackled hook across the surface, and you’ll put the trout off. This situation requires precision dead drifts, often of considerable lengths. This trout may also be just as picky about the pattern itself.

READ: Troutbitten | What Moves a Trout to the Fly

Selectivity, then, is not always about the fly. It’s how the fly is presented and for how long it is presented. Also, the same trout will show different tendencies, depending on what kind of water it is holding and feeding in.

These same concepts easily carry over to the nymphing game, where a dead drift is often necessary but not so often as critical — especially the drift length. The waters where we tend to throw nymphs have more currents that move faster. And if nothing else, the three dimensional nature of presenting a nymph allows for a little more forgiveness from the trout. Because with more complex currents come smaller windows. A trout may be watching for food in a square foot and nothing larger. And with faster currents, I suspect the windows are even tighter. How important, then, is a dead drift here? It’s an excellent goal, but given the complex nature of currents underwater, we should all be thankful that the trout’s windows are smaller, because perfect dead drifts underneath are rare.

READ: Troutbitten | Nymphing: Three Ways to Dead Drift

Of course there are times when trout seem to be looking upstream in one underwater-lane a long way. And where that is possible, I have no doubt that a trout expands its window, simply to enhance its opportunities.

We can’t know anything for sure, when it comes to why and how trout receive our flies. But it helps to think things through, to gauge the trout’s response and consider the variables of its position.

Our small-window trout isn’t discriminating about the quality of drift, but it is picky about the location.

And our larger window trout might be extra-selective about the quality of the dead drift, but it’s probably less picky about the exact location.

Why did the trout eat the fly? Was it drifting naturally for a long distance, or did it enter the tight window of a waiting wild trout?

Fish hard, friends.

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Enjoy the day.
Domenick Swentosky
T R O U T B I T T E N
domenick@troutbitten.com