Where To Find Trout In The River

In this section we describe where to find Trout in the river. This will help you identify places to fish and give you a better understanding on where fish live and feed in rivers.


The map begins with a riffle, because riffles are where rivers find their life. Riffles are defined (for fishing purposes) as a shallow (0-2 feet) higher gradient section of river, running over cobble, gravel and small rocks. They’re vital to river health for two reasons.

Photosynthesis, the bedrock of any ecosystem, can only occur in shallow water. Water, with its density and suspended particulates, removes colors from the spectrum as it gets deeper. Plant life needs the entire light spectrum to thrive. All that slippery moss, algae and other aquatic greenery we slip on wading the river is food for all aquatic insects. Additionally, because of the makeup of the bottom in riffles, there are uncounted spaces aquatic insects live amongst the cobble and rocks. Riffles are a river’s prime breeding ground for a healthy insect population and a great place to find trout.

Riffles are also the river’s aerators. As water bounces and rumbles through the riffles, the uneven bottom creates gurgles, blorps and other flow impediments. These impediments break the surface film, create bubbles and oxygenate the river, just as an aerator does in an aquarium. While vital at all times, it’s crucial in the summer months, when warmer water holds less oxygen. Riffles, due to their makeup, put life giving oxygen in the water, allowing all organisms, from the smallest to the largest, to survive.

From a wading standpoint, riffles are an excellent place to access or move along a river. They are shallow, and while moving quickly, they have a firm bottom and apply less pressure to the body. Just as a heron has long, thin legs to resist the push of the current, wading in shin deep water is much easier than wading in thigh or waist deep water.

Riffles provide prime lies for many fish, mostly on the smaller end. Lots of food, the broken surface helps keep them hidden, while many current obstructions provide haven for the trout.

100 Ping Pong Balls

Imagine if you dropped 100 ping pong balls in a straight line across the river right at the end of the riffle on the map. The fastest ping pong ball wouldn’t have moved 5 feet before NONE of them would be even with any other. The ping pong balls on the river’s edge would be almost stationary, while the ones in the middle would be flying along. As they hit obstructions in the river, they would change course, and start to follow the seams in the river. The imaginary ping pong balls are a visual clue to how the water is moving on the surface, and very often below, in a river.

Think of each ping pong ball as a visual pathway to the conveyor belt of food that is a river. A free floating insect, submerged or floating, follows the same path as the ping pong balls. In a very real sense, if you track the balls, you track the insects

Air bubbles on the surface, or foam, are a non-imaginary way to read how the water is moving at the surface. The bubbles follow the currents and seams of the river, marking their path like an easily seen path through the woods. There’s a saying from the best fly fishing guides in Missoula, Foam is Home. Where bubbles congregate, so do the bugs. Use the foam lines, use the bubbles, to mark the path of the river. More bubbles = more bugs. This is a great rule of thumb to follow when tryin to figure out where to find trout in the river.

Rock Garden

This is mostly a Clark Fork River formation, but can be found on any river in the area. A rock garden consists of rocks from cinder block to suitcase size stacked up along the banks of the river, with water flowing over them. This is a very safe haven for trout, as the rocks protect them from overhead predators. Simply put, any diving bird (Eagle, Osprey, Falcon) that tries to take a fish from a rock garden is quickly removed from the gene pool! Those birds are accurate, but not THAT accurate! Rock gardens are also excellent habitat for insects, and the trout are well fed in these places.

As an aside about the Clark Fork or any other large trout river. It’s very tempting to wade as deeply as you can and start throwing towards the enticing water in the middle, with its big boulders and easily recognized seams. NOT what you should be doing. 80% of the fish in a river live within 15 feet of the bank. Trying to get your fly down in 10 feet of roaring water is not the easiest thing to do when fly fishing. Don’t be enticed by the “easy” looking water in the middle. Work your fly in the rock gardens and other structure found on the edges of the Clark Fork River, you’ll be much more successful. Again, true of any large river, not just the Clark Fork.

Rock gardens are prime lies because the rocks break the current, the bottom around the larger rocks provides good insect habitat, while the larger rocks provide protection from airborne predators. Since most rock gardens are found near the shore, there’s an added bonus of terrestrial insects finding their way to a rock garden as well.


Boulders, or any large rock in a river, are excellent structure for trout. Boulders provide a significant current break, providing a resting place in the middle of a faster current. Boulders channel all the currents running into them to either side, condensing the insect population from the width of the boulder to a 3 inch path that comes around either side of the boulder. The trout sit behind boulders in relative calm, then dart out to feed on the insects whooshing by. The back eddies formed by larger boulders can create places with almost no current, and are favored lies for bigger trout. It can be tricky getting a good drift directly behind a big rock or boulder, but there are always trout there, taking advantage of the break in the current and abundant food.

Boulders offer great buffering from the current. They direct all the food that hit their fronts to the sides, and have the depth behind and in front to provide protection from predators. Yes, under stress a trout will flee to the front of the boulder, to get away from predators. When asking most anglers where to find trout in the river, this is often their first thought.

Shallow Shelf

Shallow Shelves are easily identified on a river as a place where light water pours into darker water. An abrupt distinction between light and dark water is always a good thing to look for in a shallow shelf. As said before, photo synthesis takes place in shallow water, and shallow shelves are no exception. What makes shallow shelves such good habitat for trout is the drop off. As insects become dislocated from the bottom, they float beyond the safety of the shallow shelf. Once past, they precipitate into the slower, deeper water found just below them. That’s where the trout are, waiting for food and using the shelf edge as a break against the current. When fishing a shallow shelf, always start your fly in the shallow section, and allow your fly to float/descend naturally off the shelf and to the waiting trout. Casting directly into the dark water misses most trout, and appears unnatural.

Shallow shelves have abundant food due to photosynthesis, with the safety of depth right behind the trout in the darker water. The current break depends on the abruptness of the change from light to dark- an abrupt change offers more buffer while a gradual change offers less.


Logs provide many things to trout, especially the log in this diagram. Logs are round (it’s why you’re reading this, for info not available anywhere else!) and as water cascades into them, it’s deflected above and below the log’s center. The water pushed below the log digs out a small trench beneath it, offering the trout protection from predation from above. A great hiding spot for trout.

Logs are a natural material, and as such, are utilized by species like ants and beetles as food and shelter as well. These terrestrial insects will often find their way into the water. A trout living by a log quickly learns these insects are food and take advantage as they enter the water.

This specific log is positioned in such a way that many current seams hit it broadside, and then float along the length of the log, coming off the curved end of the log at the far left. This log is a funnel for all those current seams, herding the water and its free-floating insects along its length. Look for a big trout to be situated at the end of this log. It’s close to lots of food (Need one of a prime lie), it’s close to shelter (Need two of a prime lie), and it provides protection from the current (Need three of a prime lie). This is how you put together those three needs to find a place that will hold bigger trout.

If you come across a log in or along a river, make sure you fish the length of the log before you decide to jump on it to start casting or wading! When you step on a log, the vibrations from your feet will reverberate through the log, notifying every fish near it that you’re there. Not a good start to catching fish- spooking them before you even begin!

Logs are great for protection from predators, and offer varying degrees of current buffer depending on their angle in the river. It depends on their location if they are close to food or not.

Under Cut Bank

Under cut banks are created when the river current runs into the shore, but doesn’t come over the bank, digging out a space underneath. An undercut bank provides impenetrable protection from overhead predators, and depending on how far under the bank it goes, a definite break from the current. Under cut banks won’t always hold many fish, but the ones they do hold tend to be very big.

If you suspect that you’re coming to an undercut bank when walking on the shore, make sure to walk far around it. If you walk to the edge of the under cut bank to peer over, your footsteps have alerted any trout underneath to your presence. Keep a good distance away, or even better, try to approach it from above or below for stealth.

Undercut banks are the best defense against predators. They also offer good current buffering, which increases the more undercut they are. Very little photosynthesis goes on in this low light situation, so trout need to leave the undercut bank to feed. Undercut banks are more often a haven for larger fish when not in feeding mode, so it’s worth running a fly here to see what happens. You may not hook anything, but if you do, it will be well worth it!

Deep Dark Hole

You look at this deep spot in the river, and know fish live there! But not as many as you think. The depth/darkness of deep dark holes mean very little photosynthesis is going on, which means very little food is found there, other than the food the current brings. So not a lot of fish.

However, deep water is excellent protection from most predators, and often very slow near the bottom. It provides safety with little energy expenditure. While deep dark holes may not hold many fish, the fish they do hold are big. It pays to get down deep and fast in these sections of the river to see what’s there!

Depth is great protection from predators, and quite often the water is moving slowly enough on the bottom to be a good resting spot. They can be a little shy on food, so trout here will venture out to feed. Like the undercut bank, this is not a feeding lie, but is often home to large fish resting between meals


Trees along the bank provide many things to trout. Overhanging branches provide protection from overhead predation, because nothing can swoop down through them. The branches are also home to many terrestrial insects like ants, beetles, cicadas, katydids and a myriad of other life forms. These insects find their way into the river, and trout living there rapidly learn they are viable food forms.

Trees also provide shade, which can be very important on a sunny day. Trout have no eyelids, and when the shade from a tree is extending over the water, it provides a place where the trout can sit in comfort and feed. This is especially true of Brown Trout, whose coloration is suited to darker places.

Trees offer protection from most overhead predators, and often provide terrestrial food in the warmer months. It depends on the river structure if there’s a current buffer for the trout.

Back Eddy

Officially known as gyres, back eddies are a fly anglers dream and curse. Conflicting currents make back eddies difficult to fish, but they always hold lots of fish, and one of the best place to find trout. A back eddy is a depression in the shore of the river where the water recirculates. They look like the top of a latte after it’s stirred, with water flowing in a circle inside the river bank depression. Any insect entering the back eddy recirculates, giving trout multiple chances to find and eat it. Back eddies become home to a lot of food, and lots of trout.

Back eddies are tricky to fish. With so many different current directions, it’s difficult to know where the trout are and which direction they’re facing. Yes, trout face into the current in a river- a back eddy has currents going in all directions. It’s also very difficult to geta drag free drift in a back eddy, as the multiple currents rapidly remove slack from any cast, creating drag. Back eddies are a home to many fish, and many frustrations as well. They’re always worth fishing hard.

Back eddies are chock full of food, and vary in trout safety depending on depth. Because the current is often running counter to the river direction, it can be very gentle, offering an easy place to rest.

Grassy Banks

Grassy banks offer a lot of what trees offer, only on a smaller scale. Protection from overhead predation, food sources that live in the grasses and shade when the sun is at the correct angle.

Many grassy banks are found above fairly sheer mud walls. The mud walls offer the trout protection at their base as well. The grass above and the wall face provide good habitat for trout.

Grassy banks offer protections from overhead predators. Depending on location, they may offer a current buffer. Some terrestrial food will be supplied in the warmer months, but again, it depends on location.

Diamond Chop

Diamond Chop is found where a faster current goes by a slower current, often at a curve in the river. These spots are great places to find trout in the river. The faster water pushes into the slower water, creating a disturbance on the surface. This surface disturbance is very difficult for predators to see through, offering quite a bit of cover in what would otherwise be a fairly exposed lie.

It’s also where a fast seam butts against a slow seam, which is exactly what trout are looking for. They sit in the slower current and feed in the faster current, conserving energy while taking in calories. It takes a bit of experience to find diamond chop, but once you recognize it, you won’t pass it up when fishing.

It’s not easy to see trout rising in diamond chop. You have to look for rises, unlike a glide or other flatter river section where a rise is self-evident. If a hatch is on, and you see diamond chop, stop and take a look. The rises aren’t easily read, but if you look long enough, you’ll see them.

By definition, diamond chop is a current break- allowing trout to be in slow water feeding in fast. The choppy surface deters predators, and the food supply is steady with the faster currents.

Feeder Stream

Anywhere a feeder stream enters a larger river, there are trout. The feeder stream brings a new source of food into the river, and trout stack up just below to feed. Feeder streams can be anywhere from 3 foot wide rills to larger streams entering the river. The same rules apply.

Feeder streams often provide an environmental change as well. In winter, a spring fed feeder stream may bring relatively warmer water into the river, allowing a trout to be more active in feeding. In high summer, the feeder stream may be cooler than the main stem, and again help spur on the trout’s metabolism. Never pass by a place where water enters a river- that’s a great place to find trout in the river.

Many streams entering a river will have cleared out a deeper channel below them, which trout love for safety. They provide a new stream of food, and depending on location, may have good current breaks.

Rip Rap Wall

A rip rap wall is used to keep the river in place near a road or railroad track. They stop erosion and keep the river “on course”. Rip Rap is made up of fist to soccer ball sized rocks, all piled up along the bank. These rocks provide billions of places for insects to live, and trout are there for the insects. Rip Rap is found in places where the current pushes against the bank. The current also provides a new source of food. While not a natural feature of a river, rip rap walls have food and shelter for trout, and if you come across one, fish it well.

Rip Rap walls offer so much food, and quite often rocks have come off the wall to create current breaks on the bottom. Being man made, they are usually fairly deep, providing protection.

Random Map Notes

This is a stylized conception of a river. It is not a blue print for how it has to be. You can have trees over a back eddy. A riffle can have overhanging grass, and logs can be anywhere in the river. Boulders can be above riffles, as well as below, and a shallow shelf can be found amongst boulders. This map is just designed to show you the different places of where to find trout. You’ll need to spend some time on the water to start identifying the places where trout live.

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