Editor: Mark

Part 2: What Trout Eat—Know Your Water

In Part 1: What Trout Eat—Know Your Bugs, you learned the primary food sources for trout. Now that you understand what trout are feeding upon; and now that you have the general knowledge to identify these insects and know what sort of imitation to present to the fish, you are ready for the next step: learning where to put those tantalizing morsels so they sweep right into the fish’s feeding lane.
Let’s talk about the makeup of a river or stream. I find it interesting that virtually all creeks, streams, and rivers have essentially the same makeup, just scaled to match the size of the river. Water flows through these places in basically the same ways and trout hold in these waters in the same ways.

how to read trout stream
how to read trout stream

Refer to this picture as I discuss the parts of the stream and where the trout hold. Let’s take the callouts in order, left to right.
Eddy: An eddy is an area of the river where structure such as an indent in the riverbank, a log, or a large boulder blocks the current flow and influences its direction. Directly downstream of the object, a pocket of swirling water will form opposite the main direction of current flow. Trout love eddies because they funnel and trap insects drifting by in the current. Look for foam or bubbles collecting on the surface where the main current meets up with the swirling water and place your casts there.
The boulder above the word “Eddy” funnels through a narrow chute just above the “Y” in eddy. The main channel is marked by the white water. The backward flowing water follows the word “Eddy” back toward the boulder at the head of the chute. Fishing upstream, you would fish the deeper seam at the edge of the whitewater, staying well back so that the fish in the eddy do not see your movement. You can then turn your attention to the eddy and even scoot to the left to take advantage of a better drag-free drift from that angle.
Run: Though hard to see in this photo, a run is an in-between zone where the water becomes deeper and the current is more uniform. You cannot see clearly, but the channel between the boulders marked run is a deep seam of slow-moving water. Trout can hold on either side of the boulders, in the bottom, waiting for a snack to come by. I love to pop a dry fly against the side of the rock in these circumstances, letting it fall upon the water and oftentimes an instant strike as the trout comes up aggressively.
A run is usually up and down the river (while the little one noted above is actually perpendicular to). One of the top places to look for trout in a stream is in a run. Trout like the shelter provided by deeper water and the proximity to an easy meal. Fish often suspend at the edge of the current or lie along the bottom eating insects that are carried downstream out of a riffle.
Riffle: A riffle is a rocky, shallow area in a stream where water cascading over rocks creates a noticeable surface disturbance. On the larger rivers a riffle can run more than a hundred yards. On smaller rivers, the riffle might run 10 or 20 feet. To identify a riffle, look for a choppy surface or whitewater spilling over shallow rocks into deeper water. Many many good fishermen completely underestimate the riffle. They hurry from pool to pool, walking right through the riffles and unknowingly pushing fish as they go.
A good riffle will fulfill all of the basic needs of a trout. The shallow, highly oxygenated water is a perfect environment for the insects trout eat. Boulders and rocks create plentiful hiding and resting spots. Deeper water downstream gives trout rest and security. Fish the riffles.
Tailout: A tailout is a shallow, flat section at the end of a pool before the water spills over into another riffle. Where the water becomes shallow, a natural funnel is formed that brings anything drifting downstream right to the fish. Tailouts can oftentimes be very shallow water. Sometimes the tailout happens at the edges of the stream, in the shadows. I’ve often caught the largest fish of the day in a tailout, so shallow that the water scarcely covered the dorsal fin.
Pool: A pool is the deepest portion of any given section of river with the slowest current. How many times have you snuck to where you could see that big bad boy down there and you just could not figure out how to get down to him. Sometimes you can’t get the imitation down to the fish, and sometimes the fish is just chillin’; he is resting and not in the mood to eat. In shallow streams, on bright hot days, pools might be the only areas that hold fish, but it is different for larger rivers.
Observe and Determine the Structure of the River
Before I show you another stream, let me emphasize that trout are patternistic; they are predictable. We can say with relative confidence that the bigger fish get the water they want. The bigger fish are going to place themselves in a position to harvest the stream. They have the bulk and the bad to claim the bread basket and chase of the smaller wannabes.
Trout are also used to being hunted. They have natural enemies and so they are natively cautious. They respond to movement. I can’t emphasize this point strongly enough: When you are fishing a trout stream you are hunting. Keep low. Wear neutral clothing. Avoid quick movements and stumbling, splashing, sloppy stalking. As I have taught my sons to flyfish, I have emphasized the importance of learning the roll cast. Avoid false casting. Fishermen make too much of the false cast. I too often see someone whipping their line back and forth in frenetic fashion without realizing they are spooking fish. This holds especially true on well-fished rivers. Trout are smart and they know what it means to see lines whipping back and forth, shadows, and flashes or movements as they sit in their feeding lanes. Be cautious or you’ll ruin the fishing before it has begun.
Let’s look at another stream and talk about the kinds of structure we find in most streams and what it means to the fish.
This second picture is of a smaller stream. You can see that it is cascading, coming quickly downhill in a pattern of riffle and tailout to pool, repeated every 30 yards or so. I chose this example for the trees. This picture is in the middle of the day where the sun is directly on the water. But earlier in the day, or later, and everything changes. Trout that might hold more in the deeper pools in the middle of the day will often move to the edges and to the riffles early or late.
I have too frequently spooked fish from the shallow riffles in my haste to fish the bottom of the pool. The fish you spook in the riffle almost always run away from you (up into the pool you’re approaching). That makes for a frustrating day on the water.

reading a trout stream
reading a trout stream

I’ll close with comments on three characteristics of trout streams and rivers:
• Obstructions Any object that impedes the current flow could hold trout and is worth investigating. Place multiple casts upstream, to the side, and downstream of the object for a shot at any fish that may be sitting there.
• Changes. Gravel bars, bushy overhangs, shelves, bends, holes, and other notable changes are great places to look for holding trout.
• Seams. A seam is anywhere two different speeds of water meet. Trout like seams because the joining currents create feeding lanes that collect drifting food. With experience you will be able to detect seams as subtle lines along the surface where slower current butts against fast. Watch the current carefully as it flows over and around structure.
Reading the water isn’t just about where the trout are holding, it is also about knowing how the seams and currents of water intersect. When you make a cast, you will always need to know which way to mend your line and how much to keep it in the feeding lane for the longest possible drift. When you see a seam it holds the promise of fish, but it is also sending a warning that you better know how to put that fly on the water or it will start skating on your and that’s pretty much the end of that.
There you have it: know your water. When you have the time, conclude this three-part series by reading the next installment: Part 3: What Trout Eat—Know Your Technique

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