Where a trout wants to be and why
The previous lesson covered seams, riffles, and slack water — the shapes moving water forms. This lesson places a fish within those shapes, because the shapes matter only insofar as they predict where a trout will hold.
Two variables govern a trout's choice of position, and both operate continuously. First, energy expenditure: how much effort it costs the fish to hold a given spot. Second, predation risk: how exposed the fish is to herons, ospreys, and anglers while it holds there. Every position a trout selects is a solution to those two variables. Learn to evaluate a piece of water by the same two criteria and you can read it with reasonable accuracy.
Low energy cost
A trout will not fight the full current continuously; doing so burns more energy than feeding returns. It therefore seeks slow or slack water positioned close enough to fast water that drifting food remains within reach. This is the function of a seam — the boundary where fast and slow water meet. A trout holds on the slow side of the seam, moves laterally into the fast lane to intercept a food item, and returns. Displacement is minimal and the fish feeds at low cost.
The same principle applies at a rock. The holding position is not on top of the rock but behind it, or in the cushion of slack water the current forms directly in front of it. In either case the rock breaks the current and the fish occupies the resulting calm pocket.
Low risk of getting eaten
Beginners routinely overlook this variable. A fish holding in bright, shallow, flat water is fully exposed to every predator in the canyon. A position with abundant food will still hold no fish if it offers no protection. Trout require cover, and cover takes several forms: depth, a riffle that breaks up the surface, a shaded bank, a submerged log, or a boulder. The common assumption that trout hold in open, attractive water is mistaken, and it accounts for a great deal of unproductive fishing.
Combine the two variables and the productive positions become predictable: the edge of the fast water, adjacent to a current break, with enough depth, shade, or surface disturbance that the fish is not exposed. That is effectively the entire map.
A way to practice this without getting in the river
This pattern can be modeled at home, and I recommend it, because the mechanics are easier to observe when nothing is moving quickly.
- Fill a kitchen sink or a large tub with water.
- Place a rock or a coffee mug in the center.
- Turn on the faucet to a steady trickle, offset to one side, to produce a small current past the object.
- Observe where the water decelerates. A calm pocket forms directly behind the mug. A thin calm seam typically forms along each side as well, where the fast water sliding past meets the slower water deflected around the object.
Those calm zones correspond to where a trout would hold in a real river. It is a rudimentary exercise and it is effective. I ran it with a spoon in a mixing bowl the first year I taught this class, felt slightly foolish doing so, then fished the Provo the following weekend and began catching fish behind rocks I would previously have ignored.
An observation worth stating
I will state the principle I return to repeatedly: reading water outperforms expensive equipment consistently. I once watched an angler in new waders, with a rod that cost more than my first car, cast well into empty water for an hour, while a child in tennis shoes ten feet upstream took two fish from behind a rock the size of a soccer ball. The child was not casting well. He simply placed the fly where a trout would hold. That is the decisive factor.
This connects to Pamela. I taught her the clinch knot several classes ago and she learned it faster than I did, which I told her directly, in front of the group, because it was accurate. I then spent roughly a week feeling competitive about a student outpacing my own learning curve — an unreasonable response for a grown man, which I mention only because it is true. Pamela handles the knot well. You will too. What determines whether you catch fish is whether you place that knot, and that fly, in a position a trout would actually select.
Before next time: run the sink or tub exercise once, even for two minutes, and come to the next class prepared to describe where the calm zones formed.