Water poured over moss covered stone and into the plunge pool below. I cast my line into the swirling current and watched as my indicator disappeared into a churn of bubbly foam. Instantly it was spit out into the center of the pool where it caught the tongue of the main current and began its drift downstream. I starred intently at my indicator anticipating the strike. I couldn’t see the fish, but I knew they were there.

Trout have a system for how they adapt to a river and though these behaviors can vary somewhat between seasons and species, there are certain patterns that stay consistent regardless of the water or location. From where trout hold and feed in a river, to where they go for shelter and rest – trout do things instinctively for survival and they do it over and over again. These common threads give us data we can learn from and hold unto as we make decisions regarding how to read a trout stream. They are far from absolutes, but they are breadcrumbs for us to follow as we continue to hone our trout finding skills.

Trout Lies
There is a saying that 90 percent of the trout reside in 10 percent of the river. As strange as this may sound it is true and due mainly to the fact that trout are super selective when it comes to their habitat. Though they are simple creatures with very primal needs they are extremely particular regarding where and how they get those needs met. They are efficient survivalists who know how to make the best use of their energy and resources. Because of this only the best water will do.

This top-tier water can be broken into two main categories, prime lies and secondary lies. No, we aren’t talking about the kind of lies we tell our buddies after a day out on the water. A trout “lie” or holding area is the type of water a trout chooses to occupy or feed in.

A trout lie or holding area that meets a trout’s basic needs (food, oxygen, protection from predators, and rest from the current) would be considered a prime lie. This type of water would be a trout’s first choice when it comes to location in the river. The largest and most dominant trout usually occupy prime lies.

A runner up to a prime lie would be a secondary lie. A secondary lie would be the type of water that meets at least two of these four basic elements. It can be broken down into two sub categories, “feeding lies” and “sheltering lies”. A feeding lie offers food and rest from the current, but no protection from predators. A sheltering lie offers protection from predators and rest from the current, but no food.

Depending on need and availability, trout will focus their attention on finding either prime or secondary lies in a river. They will ignore the other 90 percent. We should too!

Anatomy of the River
What does the river look like above and below the surface? Does it contain boulders, trees, or man made structures? How does one river feature interact with another? All these factors contribute to the character of a stream and how it behaves. Being able to identify these different features, as well as understanding how trout respond to them, is key in learning how to read a trout stream.

A typical river is made up of the following distinct features: riffles or rapids, runs, pools, pockets, seams, shelves and tailouts. These are the main areas in a river where trout will migrate when searching for prime or secondary lies.

Riffles/Rapids –  In general a riffle or rapid is where everything starts, it’s the part of a stream characterized by shallower, fast moving water. A riffle can be a short or longer section of river where the current is broken up by rocks and boulders. Varying in depth, riffles can run from several inches to several feet deep, depending on the size and flow of the river.

From a trout’s perspective a riffle is probably one of the most highly sought after sections of the stream. The turbulent nature of a riffle makes it a rich resource for food as movement churns up bugs from the below rock and sediment and sends it downstream in conveyor belt fashion. This agitation also creates tiny air bubbles in the riffle that provide a high concentration of dissolved oxygen, a bonus for trout when water temperatures are high. For fish looking for shelter, the broken water also acts as camouflage from prey, and for those in search of rest, the high quantity of rocks and boulders along the river bottom can offer a break from the fast current.

A riffle would be considered a prime lie for trout in the spring and summer. If a riffle is only a few inches deep it would be considered a secondary lie… a feeding lie in the spring and summer.

Runs –  A run is a deeper stretch of water, usually just below a riffle, where the current is moderate and the surface is slightly broken or choppy, but more uniform than a riffle. Runs are usually straighter sections of river still containing large boulders or underwater structure. They often connect riffles with pools.

From a trout’s perspective a run is one of the more key sections of a river. Because of its close proximity to a riffle a run is usually high in oxygen content and the slower current makes it the perfect holding area for trout looking to sip bugs from upstream. The deeper makeup of a run makes it a great place to hide from predators, especially if the above riffle is on the shallower side.

A run would be considered a prime lie for trout in the spring, summer, fall and winter. If more shallow or absent of surface chop it would be a secondary lie… a feeding lie in the spring, summer, fall and winter.

Pools –  Pools are the deepest and slowest portion of the river. They are sometimes found at the end of a run or along the outside of a river bend where the river bottom gets dredged during high water. Some pools are created by water flowing over logjams or boulders. Over time the downward force of the water carves impressions into the riverbed leaving a deep pool behind.

From a trout’s perspective a pool is more of a place to find shelter and rest then anything. Most pools just don’t provide enough current to be a reliable source for food. If the pool though is at the base of a spillover or waterfall (plunge pool) an effect similar to a riffle can occur as the faster water stirs up bugs and creates more oxygen for trout. Another instance when pools can become a feeding area for trout is if there is a hatch coming off. When this happens pools are the perfect setting for trout taking emergers or adults from the surface. One last thing to consider. Even if trout holding in a pool may not be in feeding mode, a well placed baitfish imitation may be too big a temptation to pass up. For this reason always think of streamers when it comes to deep dark pools.

Pools would be considered secondary lies in the spring, summer, fall and winter… sheltering lies in most situations. Exceptions would be if there is a hatch coming off, then a pool would be a prime lie temporarily. If a pool is below a spillover or next to riffles or faster moving water, it would be considered a prime lie year round. In winter months, when trout move out of the faster water and into the deeper sections of the river, a pool could become a prime lie as well.

Pockets –  Pocket water is usually found in fast to moderate sections of the river where structure like rocks, boulders and logs create a break or cushion from the river’s current. In essence a pocket is an area of slower water that is formed either in front of or behind an obstruction. Pockets in front of an obstruction are formed when faster water bounces off the face of the obstruction and collides with the forward-moving water. Pockets behind obstructions are formed from back eddies that swirl in differing directions and thus slow the water.

From a trout’s perspective pockets are an ideal place to hold and feed. Since the water is often more turbulent, trout get a good boost of oxygen in the water. With the faster movement there is a continuous flow of food and the structure provides rest from the current. If the water is broken enough, which it usually is in faster water conditions, a trout will get shelter from predators too.

A pocket would be considered a prime lie in the spring, summer, and fall. If shallow and less broken it would be considered a secondary lie… a feeding lie in the spring, summer and fall. If a pocket is deep enough and in moderate current it could be a prime lie in winter as well.

Seams –  A seam is just a portion of water where the fast and slow currents meet. This could be either a vertical seam or a horizontal seam. Taking a three-dimensional approach – vertical seams run alongside each other and horizontal seams run on top of each other. Think about cutting a birthday cake. If you cut the cake from top to bottom, leaving two pieces side by side, you would have a vertical seam. If you cut the same cake through the middle, leaving a top and bottom half, you would have a horizontal seam.

Let’s talk vertical seams first because they are the easiest to see and identify. A vertical seam would be any place where differing water features (with differing speeds) are adjacent to one another. So where a riffle or run meet alongside a pool or pocket, these areas would form touch points or seams where fish would hold in the slower water and feed on bugs drifting by in the faster current. Pretty straight forward.

Horizontal seams are a bit trickier. They are the ones we can’t see from above, but they are just as important. As a general rule water on the surface of the river moves faster than the water toward the bottom, creating a seam in between. Trout will often hold in the slower water toward the bottom of the river and come up to grab insects floating by in the faster water overhead. Think about the two layers of the cake, one on top of the other.

Seams themselves aren’t considered prime or secondary lies, but the water on either side may be. Since trout are continually looking for the path of least resistance, prime or secondary lies will always be on the slower side of the seam. Note: The key to fishing a vertical seam is to get as close as possible to the slower water without impairing or slowing your drift. A tight line technique in these situations can be a deadly tactic.

Shelves –  A shelf is a drop-off along the river bottom formed by sediment or rock. Anytime you see a shelf you know a horizontal seam is present. Most times identifying a shelf can be difficult and if the water is murky or choppy it can be impossible, but the more you fish an area the more you will learn where the shelves are. Look for areas of water that go from light to dark, these are signs of a shelf below. Also observe the river bottom at lower flows. This is a great way to identify shelves in a river.

A shelf, if the water is broken and deep enough, would be considered a prime lie year round. If the water is shallow and clear it would be a secondary lie… a feeding lie only in the spring, summer and fall.

Tailouts –  A tailout is the section of the river toward the tail end of a pool or run where the river becomes more shallow right before spilling into the next riffle or rapid. Tailouts usually tapper down into more narrow passageways.

From a trout’s perspective a tailout is a key place to hold when food is abundant. Because a tailout offers a narrow area with slower current trout have the perfect opportunity to feed with little effort. The problem is most tailouts lack shelter or cover. Because of this trout will be wary of feeding in a tailout unless they have an easy escape route to deeper water or the food is so plentiful it’s worth the risk.

A tailout would be considered a secondary lie… a feeding lie in the spring, summer and fall.

Conclusion
How trout behave in relation to their habitat is a complex thing. The more I see the psychology and science behind this relationship, the more I’m amazed at the beauty of the one who designed it.

As a fly fisherman, each time I step into the river I’m given the opportunity to watch and observe these intricacies firsthand. When I step out at the end of the day I’m given the opportunity to reflect on what I’ve learned.

Have I fooled a trout or two along the way?

Hopefully!

If not, I’m still blessed to have walked with the fishes!