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The first rule of fishing is “fish to fish.” By this I mean: cast your line where you know (or strongly suspect) a fish might be. There is no point in casting to where there are no fish. This may seem obvious, but many fishermen don’t seem to get it. If I want to actually catch a fish, there must be at least one fish in the vicinity of where I am casting. Simple enough.


But, instead of determining where the fish are holding and what might interest them, some fisherman choose a pool with little thought and blindly cast in the hopes of happening upon a fish. Or they believe that a fish might just wander by, perhaps on a Sunday stroll. When I was young and didn’t know better, that is exactly what I did. Needless to say, I didn’t have much luck using this low percentage strategy. 

Fly-fishing: Habits of Native Brook Trout

From Chapter Of Wild Rivers and Wild Trout by Guy Van Wie


















Knowing where fish are hiding, and, even better, actively feeding, is more than half the battle. If I don’t know for certain where they are, then I should have a pretty darned good idea based on past experience. Even if the trout are right there where I think they are, they might not be interested in taking a fly. But knowing a trout is there is better than the alternative, which is pure guesswork. Or dumb luck.


Resting on the bottom of the stream among the shadows, trout remain almost invisible even to a seasoned fly fisherman. They are very good at hiding because there are many hungry predators with a sharp eye and lethal tactics—otters, kingfishers, mergansers, mink, herons, osprey, and eagles, as well as other bigger fish. When a trout rises to investigate a fly, it sometimes turns a bit, “flashing” its lighter belly. That flash can be enough to give away its hiding place. Once I know a fish is interested in my fly, I just have to figure out what exactly I need to do to get that trout (or its neighbor) to take my fly with conviction.


Light and shadows, temperature, flow, cover (rocks, logs, cut banks, or other structure), and food availability are the main factors that determine where a trout will be. Ultimate survivalists, trout need oxygen, food, and cover, in that order. Their existence is all about optimizing those factors while expending less energy getting the food than the amount of energy the food provides. 


Trout prefer cooler water, between 40° and 60°F. Cold water contains more oxygen than warm water. Trout seek water with higher oxygen levels either by moving to areas with cooler water temperature or where the water is physically aerated, such as beneath a small waterfall. If the river water warms up on a hot day, as it does quickly on the Swift Diamond, the trout will hunker down where groundwater (averaging 42° to 52°F in northern New Hampshire) seeps in through the gravel, usually in the deeper holes.


For food, there are several options: insects (either aquatic or terrestrial of various types and life stages), other smaller fish, worms, leeches, fish eggs, and a few other small animals, including frogs. A big trout might eat the tiniest insects and swallow something as large as a mouse. I caught the biggest trout I ever caught (three-plus pounds) on the smallest fly I have ever used, which was about the size of a flea. When I netted it, the trout looked like it had a poppy seed stuck in its teeth. Smaller fish must eat smaller food, but can occasionally be quite ambitious in what size bug or fish they will go after. It’s a wonder how a little fish can get its mouth around a formidable #8 size streamer fly.

In a river, the moving current provides a traveling cafeteria line of food options that concentrate in certain places, depending on the flow patterns and eddies around rocks. The menu will include whatever small creatures are hatching, migrating, or drifting by. The trout’s main job, then, is to find a cool place with good cover from predators, with not too much current (to save energy) that’s near a steady flow that might bring food right past its nose.


To take advantage of this moving cafeteria effect, I try to place my fly in the seam that is often visible between fast water and slow water, near rocks, or above pockets deep enough for a trout to hide in. Often we “fish the foam line,” where natural foam, debris, and floating bugs concentrate into a predictable path down the stream. The trout will compete with each other for the most advantageous resting places near these fast-food locations, and dart out to take a morsel as it floats by.


As stuff passes by in the current, the trout has to decide in an instant:  is it Food or Not Food? A creature of habit and often short on memory, the fish will often choose the familiar, but may investigate new items that could be Food. I sometimes change flies five or ten times trying to find one that a trout will think is a real meal. It can be harder to trick them in clear water than in cloudy water because the trout may get a better look at the fly and easily decide it is Not Food.


Trout will often lock on to one type of bug that is most abundant, especially when thousands of that insect are hatching at once. Large concurrent hatches are a survival strategy for various insect species. If I can mimic the trout’s favorite food du jour with a specific fly, then a strike by the trout is more likely. This is called “matching the hatch.” Hitting a big hatch, as Phil and Bill Burgess did their first evening in the Grant, is a fisherman’s dream because trout will congregate into a feeding frenzy. Meanwhile I am rummaging through my vest to quickly find the right fly that looks like the natural insect on the water.


Not only is the choice of artificial fly important, so is the “presentation.” A wild trout can quickly tell the difference between a real insect drifting naturally in the current compared to an artificial fly that is dragging cross-wise to the flow because it is connected to a heavier line and rod. How a dry fly rests on the surface, or how a streamer “swims” through the current, or how deep it sinks in the water column—these are all important aspects of the skill it takes to entice a trout to take an artificial fly made of feathers, hair, and a hook. 


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