How to Fish for Trout in a River (An Angler’s Guide)

Everything you need to know about how to approach a river including where to find trout, when to target them and more.

In this post, I’ll teach you everything you need to know to catch trout in a river. We’ll look at when the best time is to target them, what techniques to use, where the trout are holding, and what trout eat.

There’s nothing more exhilarating that stepping into a wild trout river and not knowing what the day might bring. To some fly anglers, though, fishing a new stretch of unknown water can seem quite daunting.

I’ve fished for wild river trout for many years, and although there are always surprises on the water, trout can be very predictable once you start understanding their behavior. It’s this insight that will make you a better trout angler.

In this tutorial, we’ll first look at the basic drivers which determine where trout hold and the terminology around different river structure types. We’ll then look at what trout predominantly feed on and how you can effectively approach and fish for trout. 

After reading this article, you’ll know everything you need to know to find and fish for trout on a river.

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Where Do Trout Hold in a River?

I mentioned above that trout can be very predictable. With this statement, I didn’t mean that they’re boring to catch, but rather that once you understand what determines where they hold, you’ll always be able to find trout.

trout river fishing

In general, a trout holds in a specific location because of oxygen, a food source, shelter, and/or preservation of energy. As always, there are exceptions to these rules, and you should be aware of this when you’re on the water. Let’s look at the drivers in more detail.

Oxygen

Dissolved oxygen in water (which fish need to live) walks hand in hand with water temperature. The higher the water temperature, the more kinetic energy there is between particles and the better the chance for oxygen to escape. On the other side of the spectrum, the cooler the water, the more oxygen remains dissolved.

Trout, and any fish for that matter, rely on dissolved oxygen in water to stay alive. As water passes through their mouths and over their gills, a gas exchange happens and oxygen is absorbed into their blood.

When water temperatures are very cold and there’s an abundance of dissolved oxygen in the water, trout can move around pools freely. Their location is driven by other factors like the preservation of energy and food sources.

However, if water temperatures start climbing in high summer and water levels drop, dissolved oxygen levels plummet too. As a survival tactic, trout have to move into water zones that have a higher concentration of dissolved oxygen. And where might this be?

Any area where there are riffles, rapids, waterfalls, or water dropping into a pool will have a higher oxygen concentration. Trout position themselves right under the source of this oxygen, and this is why these spots are so effective to target trout.

Food Source

Oxygen is one element critical for a trout’s survival, but having enough food around is equally important. Trout are opportunistic feeders and experts at adapting their feeding and hunting styles to what the most prolific and efficient food sources are.

Later in this article, we’ll take a deeper look into what exactly trout feed on, but for now make a mental note that in order to find the trout you need to find their food.

A bubble line, for instance, is such a source of food. Any insect hatching or floating on the surface will be carried into the pool in the bubble line. This is where trout lie in ambush and simply sip their prey off the surface.

Preservation of Energy

We can’t talk about river trout and their food sources without touching on the subject of preservation of energy. Just like humans, trout burn calories in order to move around, so they, once again just like humans, try to do so as little as possible.

You won’t see a trout swimming around with its iPhone Watch tracking its steps. No, they try to save as much energy as possible.

Firstly, trout are constructed to be as hydrodynamic as possible in order to conserve energy. But if trout really want to save up on their energy bill, they need to be in slow water. But, what if their food source is moving downstream in fast water?

This gives us one of the greatest clues to where trout hold in a river. Find a spot where the trout can hide from a fast current, like in slow water or behind a rock, that meets with a fast piece of water that constantly brings food downstream to them.

You need to present your fly on this seam. The trout sit in the slow water, and as soon as they spot a tasty-looking snack, they pop into the fast current, eat it, and retreat back to the comfort of the slower water.

Shelter

The fourth factor that determines where trout hold in a river is shelter. Although trout are incredibly efficient predators and the mere sight of them will make most mayflies tremble with fear, trout are the food source for many other predators.

There’s incredible footage of trout hovering just below the surface in broad daylight and they’re so easy to spot. This isn’t always the case, but just because you can’t see them doesn’t mean they’re not there.

Trout aren’t only incredibly well camouflaged, but they also hide under shelter or cover to stay out of sight.

In a river, always fish up against bankside vegetation where the trout can hold in undercuts. They also love using shade as cover, so make sure that you fish any shaded areas on a bright and sunny day.

Not only physical structure offers cover for trout. Deep runs where you can barely see the bottom also offer great cover for trout, so make sure you fish areas where the bottom is dark or not visible.

River Structure

A river is a flowing and living body of water that exists out of many different structure types. Although it does seem very complex, and in a sense it is, we can break a river down into several major parts and work out a strategy for each one of them.

Let’s look at basic structural terminology before we learn how to approach a river and how to fish for trout in a river.

What Is a Pool?

One of the most common types of structures or water types you’ll find on a river is a pool. Pools come in different sizes, shapes, and depths, but the approach remains the same.

The section where the water flows into the pool is called the head, and where it flows out of the pool is the tail. The part in between, you guessed correctly, is called the body.

Fishing the Tail of a Pool

The tail of the pool is usually overlooked but can offer some of the best fishing. Trout love to sit right in the tail, where the water drops off into the next run or pool. The water accelerates in this area and the fish need to move fast and make a quick decision to eat the fly or not.

Many anglers struggle fishing the tail effectively because their fly line ends up stuck in the fast current as the water drops into the next run. With their fly still drifting in the slower water before the tail, the fly is dragged over the surface and is simply ignored by the trout below.

The most important thing to take into account here is line drag. Usually, the tail’s flow rate is relatively slow, but as the water drops, it increases drastically. So, if you deliver a fly in this slow water but your fly line is caught in the fast water, you’ll immediately get drag. You’ll never catch a fish like this.

You need to deliver the fly in the slow water and ensure you keep the fly line out of the fast stuff. As the fly drifts down towards you, lift your rod to lift the excess line in the air. In this way, you’ll get a drag-free drift which is crucial to entice a take.

How to Fish the Body of a Pool

After working the tail, you need to plan how you’re going to approach the main body of the pool. This approach will be dictated by structure. Look for overhanging vegetation, rocks, current seams, deep cuts in the bottom, and shadows.

Be delicate and careful in your approach and present the fly well above the desired area you want to fish, and then allow the fly to drift into the zone naturally.

How to Fish the Head of a Pool

The head of a pool is where the water enters the pool and is the area where the highest concentration of dissolved oxygen exists. In most cases, this is the honey hole area of the pool and produces the most fish.

The fast current that drops down into it gives fish cover and a fresh supply of oxygen. One of the reasons I believe the head is so effective is that fish don’t have a lot of time to inspect the fly because of the high current speed. They either need to eat it or leave it.

When fishing the head, make sure that you do so systematically. A fish will often hold in a small narrow slot, so if your flies drift just to the right or left of it, it won’t get eaten. Choose a direction that works best for the situation and work it thoroughly from one side to the other.

If you don’t get a bite with the first pass, change the color, size, or weight of your flies, and do another pass.

What Is a Seam?

A seam is the meeting point of two currents flowing at different speeds. You can think of this as a seam between two different material colors. Understanding how to fish around them effectively is vital, especially when working the head of a pool.

As mentioned earlier in the article when I spoke about the preservation of energy, trout prefer resting and settling down in slower water.

Seams offer the best of both worlds, where trout can preserve energy but have access to fast water where food is constantly flushed downstream. The trout simply dart out into the current, eat one or two insects, and return back into their lie.

How to Fish Pocket Water

One of my favorite types of water to fish is pocket water. You can think of pocket water as a combination of small or tiny pools, which can be as small as a dinner plate. Each small pocket has its own head, body, and tail, so the systematic approach remains the same.

Your casts need to be short and accurate, and most importantly, you need to be in full control of your flies the moment they land. The reason for this is that the drifts are usually very short, so you need to make the drifts as efficient as possible.

Always Fish Around Transition Lines

By transitions, I mean any change in a physical characteristic of the river. For instance, a seam, which I just spoke about, is a transition line between fast and slow water. There are many other transitions that are also good spots for trout to hold.

I treat any such transition as a structure type and work it accordingly. The transitions I look for are:

  • Differences in current speeds, like a seem
  • Differences in depths, like a steep drop-off
  • The transition line from full sun to shade
  • A transition in the color of the bottom substrate
  • The transition line between bare bedrock and a gravel bottom

Look for Foam and Bubble Lines

Keep your eyes open for distinct foam or bubble lines in a pool. These will show you the main line where the current pushes the food into the pool and is one of the most likely fish holding spots.

Work either side of the bubble line, especially with a dry dropper, and you’re almost guaranteed a fish.

How to Approach a River

With the essential knowledge of the basic structural elements that make up a river, let’s look at the systematic approach to maximize our efficiency and get the most out of a day’s fishing.

Watch the Water

When I arrive at any stretch of river, I spend a good five minutes watching the water. If there’s a hatch coming off and the fish are feeding actively, I’ll immediately start seeing rising trout.

River fishing

If the fish are holding deep, scan the pool or run from side to side, keeping an eye out for any movement or strange shadows. Look around the structure, overhanging vegetation, and deep sections.

What you’re trying to establish here is the type of water the fish are holding in. Are they deep, are they shallow, are they in the shade, or are they sitting in fast water?

The more you train your eye, the better you’ll get at seeing fish. It’s small clues, movements, and colors that give their position away. Oh yes, and make sure you’re wearing a good pair of polarized sunglasses.

Direction of Approach

Now, in which direction should you fish? I recommend moving in an upstream direction. In most cases, especially in faster-moving water, trout will hold in an upstream direction, which means they’ll face the oncoming current.

In my experience, approaching in an upstream direction means that you can get much closer to fish than walking down towards them. When you can make a cast, make one in an upstream direction and allow the flies to drift naturally towards the fish.

Once you’ve worked a pool, you can quickly tie on a streamer, like a Microbugger, and swing it downstream to make sure you covered all fish and likely holes.

Systematic Approach

One of the reasons I love fishing with competition anglers is that they teach us a lot about how to work the water systematically. In many cases, they’re not necessarily better anglers, but they catch more fish because they’re more thorough and have more patience.

When you get to a specific section of the river, whether it’s a pocket, head, or tail of a pool, it’s important to work the water very thoroughly. The best way to do this is to have a system.

I use a sweeping system where I work a run from left to right, with 5 to 10 inches between each cast and the next. On each cast, I use the same amount of line. When I reach the other side I sweep back from right to left.

Once I reach my side of the river again, I’ll give one or two steps forward and repeat the process. This is just a general system and might differ between scenarios, but you should get my drift (pun intended).

What Do Trout Eat in a River?

Once you’ve scanned the water and have a better feeling of where the fish are, you need to establish what food types are present in the system, especially if you’re fishing in a new area.

what do trout eat in a river

Yes, I know that if you chuck a sexy black Woolly Bugger at a trout, the chance is 80% that it’ll eat it. But in order for you to become a more successful angler, you need to understand what their main food sources are.

This won’t only help you tie better flies (if you happen to tie your own flies), but it’ll also help you fish them better. Let’s dive in and look at the main food sources for trout.

trout eat crustaceansCrustaceans

We’ll open the trout buffet with crustaceans. These can form a massive part of a trout’s diet, especially in slower-moving water or lakes.

Let’s look at the main species of crustaceans, imitative flies, and how to fish them.

A small scud is a great cutthroat trout foodon a white backgroundScuds

The first species are scuds. Have you ever seen how enormous the fish are in Jurassic Lake?

If you haven’t, check out the vlog series we did on this incredible location. The trout in Jurassic Lake get so big because there’s an abundance of scuds.

Scuds are small shrimp-like crustaceans between ¼ and ¾ of an inch in length, and they can be easily simulated on the fly. In general, these are slow-moving aquatic invertebrates, so it’s best to fish them very slowly on a floating or intermediate line using the wind to drift them along or with a very slow figure of eight retrieve.

A freshwater shrimp in a white backgroundFreshwater Shrimp

Freshwater shrimp are slightly larger in size than scuds, and some species can attain lengths close to 2 inches. They also occur in very slow-moving sections of rivers and lakes.

I personally only fish a freshwater shrimp pattern if I know that the trout in that piece of water have an acquired taste for them.

huge crayfish on a white backgroundCrayfish

Endemic crayfish can be a good indication of water quality and the overall health of an ecosystem. Unfortunately, a lot of endemic crayfish around the world are under severe pressure from poor water quality and invasive crayfish species.

Whether you have invasive or endemic crayfish present in the water you fish, large trout go mad for them. There are a ton of crayfish fly patterns out there, and these flies can easily be used for your bass fishing sessions.

Crayfish move slowly on the bottom but can move with great speed when chased, so keep this in mind when you retrieve the fly.

Mammals

Trout are very opportunistic and don’t necessarily stick to food sources commonly found in the water but also prey on mammals.

The main target here is small rodents like mice that accidentally fall into the water or are crossing from one side of the stream the other. Whatever the reason they find themselves in the water, large trout are known to eat mice without any hesitation.

As far as trout flies go, mouse patterns are large, have a ton of movement, and float on the surface. Cast the fly up close to the bank or any exposed structure and retrieve it relatively fast. It’s a good idea to up your tippet size here, as the takes can be quite explosive.

Amphibians

Another food source that trout love but we as fly anglers very often forget is amphibians.

Although adult frogs could be a food source for larger trout, tadpoles are a much more common food source for trout. Tadpoles can be very abundant during certain parts of the season and can occur both in rivers and lakes.

I believe this is the reason why black Micro Buggers work so well. In rivers, you cast down and across and swing the fly. Once you reach about midway through the swing, start with small quick retrieves to give the fly some extra action. Again, make sure that you up your tippet size because the takes can be quick and hard.

A close up picture of an earthworm as fishing baitWorms

Ever wonder why so many bait anglers fish earthworms? Because they just work and trout can’t leave them alone. If you’re not fishing in a competition, one of the best flies is called a Squirmy Wormy. It’s basically a round worm-like rubber tied onto a hook.

Another fly, which is competition legal, is called a San Juan Worm, which is just as effective.

Both these flies work well in rivers and lakes and are mostly fished very slow or on the drift.

Terrestrial Insects

In the summer months, there’s a lot of life moving around on the banks of rivers and lakes. Ants, hoppers, and beetles end up in the water, and trout can zone in heavily on these, especially in low-nutrient waters.

A close up picture of an ants as fishing bait on white backgroundAnts

In my book, ant patterns are probably one of the most underutilized flies. If I fish a tiny ant pattern, I tie it behind a larger, more visible dry.

When a fish rises anywhere near the sighter dry, I set, and most of the time the ant gets the job done.

A close up picture of a beetle as fishing bait on a white backgroundBeetles

Another terrestrial pattern that trout can absolutely zone into are beetles. These usually land with a good plop on the water, so be sure to imitate this when you’re fishing with an imitation.

A close up picture of a grasshopper as fishing bait on a white backgroundHoppers

Probably the best known and most fished terrestrial fly is a hopper, and for good reason. During the summer months, trout will hug an overgrown bank to sit and wait for a hopper to land on the water.

Be sure to present the fly with a good plop too, as this usually triggers a reaction from the fish. Because hopper flies are generally very buoyant, they also make great dry flies to use in dry dropper rigs.

Aquatic Insects

All the trout food sources I spoke about until now are almost “special cases.” If you related it to human food sources, they’d be something special like going out to dinner or having caviar or something like that.

But we as humans need those daily essentials like bread, pasta, fruit, and so on, and this is where aquatic insects come in. They form the bulk of a trout’s diet.

Obviously, I don’t have the time to cover all the aquatic insects out there, but I’m going to focus on what I believe are the top three: mayflies, caddis, and midges.

A close up picture of a mayflies as fishing bait on white backgroundMayflies

The mayfly is, to my mind, the quintessential fly-fishing insect, and trout feed on them throughout all the stages of the mayfly’s life cycle. I’ll run through a very basic lifecycle, and it’s a lot more complicated than I give it credit for here.

In the larva phase, the insect lives on the bottom under rocks and submerged structures. When exposed to the river’s current, they can be swept away to where they’re in the line of sight of a trout. It’s this phase that we’re mainly imitating with mayfly nymphs.

When the larva is ready to evolve into an adult, it travels from the bottom to the surface through the emerging phase. Here it’s very vulnerable to trout.

Once the mayfly breaks the surface, it hatches into a full adult, which mates and lays eggs. Mayfly dry flies like Parachute Adams or Catskill flies work extremely well when adult mayflies are around.

A close up picture of a caddisflies as fishing bait on white backgroundCaddis

Another very important insect species in a trout’s diet is caddis flies. As with the mayflies, and all other aquatic insects for that matter, trout feed on them throughout their entire life cycle.

A caddis larva looks completely different than a mayfly and actually resembles a short and stubby worm. When you inspect rocks that you’ve picked up from the stream, you’ll see small tunnel-like structures made from sand and debris. These are caddis.

Caddis hatches can be massive, and trout really zone into them once the hatch is on, so make sure you have a variety of colors and sizes to match the hatch. Great patterns for adult caddis include the Elk Hair Caddis, CDC & Elk, and the Tabanas.

midges for brook troutMidges

One of the best stillwater flies that I love using is called a Buzzer or Chironomid. They’re mosquito-looking insects and form a large portion of the diets of stillwater trout.

The most effective way of fishing for them is in the larva and emerging stage, when they start their journey from the bottom of the water column and end at the surface. Here, fishing two or three flies at a time can greatly increase your chances with a slow figure of eight retrieve.

When to Fish for Trout in a River

In this section, we’ll look at when the best time is to fish for trout in a river.

What’s the Best Time of Day to Fish for Trout in a River?

My favorite time of day to target trout on a river is during the morning. There’s a freshness and feeling of anticipation as you step inside a river, and I find that trout feed more happily. 

If you’re fishing in a deep gorge or on a river with a lot of bankside vegetation, there’s a good chance that the fishing will only switch on once the sun hits the water. We experience this on one of my home waters close to Cape Town. The fishing is usually very slow in the morning, but when the sun touches the water, oh man, everything comes alive.

On many rivers, the afternoon session takes a dip, and this is when a technique like Euro nymphing comes into its own. You’re able to deliver the flies to the fish where they’re sitting. 

From early evening to right into the dark, the fishing can pick up again. This is usually when a mayfly or caddis hatch comes off. It’s time to cut off the nymphs and tie on a single dry or a dry dropper rig.

When NOT to Fish for Trout in a River?

If you’re a catch-and-release angler like myself, the fish’s survival is of paramount importance. It’s definitely more important than our own fishing pleasure. To increase the chance of their survival, we need to avoid fishing for them in certain conditions.

The survival rate of trout after catch and release is drastically reduced when the water temperature is above 67 degrees Fahrenheit. These high water temperatures generally coincide with low flow conditions, which means the water has reduced dissolved oxygen levels. 

If you’d like to find out more about the best practices regarding catch and release and handling fish, check out the Keep Fish Wet website. Also, be sure to check out the video we did on How to Catch and Release Fish.

Conclusion

I hope that this tutorial on how to approach a river will help you out. If you’d like a more visual explanation of what I’ve gone through above, please follow the link to my Youtube video about the same topic.

Until next time!

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Disclaimer: IntoFlyFishing.com is a participant in the Amazon Services LLC Associates Program, as an Amazon Associate I earn from qualifying purchases. Please see our Privacy Page for more information.

Pierre is a fly fishing guide and professional photographer who has guided and hosted trips for top fly fishing outfitters. Since being introduced to fly fishing over 21 years ago, he has travelled, fished and guided across the globe. He has extensive knowledge on specific gear and tackle selection for various salt- and freshwater species. Some of his writing work includes blogposts for Alphonse Fishing Company and African Waters.

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