This is the fourth post in our series on how to find fish in any location. To see the rest of the posts in this series, click here.
By Spencer Durrant
One of the most amazing rivers I’ve ever fished flows through a slot canyon deep in the American West. It’s in the middle of nowhere, and it eventually merges with another, larger river, in some of the most breathtaking scenery on the planet.
As much as I love fishing there – casting a fly rod beneath sandstone cliffs creates a wonderful juxtaposition – I’m more enamored with a certain hole on the river, than I am with the incredible scenery.
The hole in question is a long, crystal-clear pool that’s home to some of the river’s biggest fish. It’s unquestionably the toughest spot on the river to fish. The trout – mostly rainbows, though a few stray browns are often swimming around – are wary, as you’d expect from fish living in what amounts to a giant fishbowl.
I caught a few fish from this pool on my first trips to the river, but never with any real rhyme or reason that made me feel like I knew how to fish a pool.
That all changed after one of my buddies took some pity on me and showed me how to fish pools. Once I understood how to fish calm, deep water like this, the pool on the river yielded tons of great fish. The key, as with almost everything in fly fishing, was learning the why behind how pools work and why fish hang out in them.
The goal of this post is to help you crush that learning curve, so you don’t spend as long as I did trying to figure out the best way to fish a pool. So, get comfortable, and get ready to learn!
What is a pool?
To make sure we’re all on the same page, let’s clearly define what a pool is.
A pool is a deep, slow section of a river. It’s usually located before or after a set of riffles. Water moves quickly at the head of a pool, slowing down exponentially as you get closer to the middle. The water picks up the pace again at the tail of the pool.
Here are a few examples of real life pools:
Why do fish hold in pools?
As with any type of holding water, pools have a few characteristics that make them attractive to trout. Let’s take a look at each of them in depth.
Slow, easy current
The biggest difference between a pool and most other holding water is the current speed. Other than the head or tail of a pool, most of the current is moving at a much slower rate than current in the rest of the river. This gives trout a nice place to hang out, sleep, and leisurely snack on whatever food drifts by.
Protection from predators
Pools – especially deep ones – offer great protection from predators in two ways. First off, the deeper water makes it tougher for predators to catch fish that are otherwise more vulnerable in shallow water. In addition, the color of deep water helps trout stay shielded from anything that might eat them.
Decent food availability
We know that trout exist to eat food. And we know trout want to expend the least amount of energy in exchange for the most amount of food. That’s why they love riffles so much – the energy expense to food received ratio is wonderfully high.
Pools don’t have quite the availability of food that riffles do, but there’s still enough in a pool to keep trout well-fed. The low current speeds also help, since trout don’t have to spend a ton of energy to eat their food.
Perfect for low-temp situations
As water warms up, the amount of oxygen in water tends to decrease. Trout make up for this by migrating to faster-moving water – like riffles – where oxygen content remains high, even during the warmest months of the year.
When winter rolls around, though, pools are the ideal place to be since they offer high amounts of oxygen, and little major current to contend with. This is one reason that you focus on fishing pools and slow, deep runs during the winter.
How to fish pools
If you look for information on how to fish pools, you’re going to come across the same general theory: you need to work through a pool in sections. The terminology might be different from writer to writer, but the idea remains the same.
To help give you the most actionable information possible, I’m relying on tactics provided by folks like Tom Rosenbauer, Devin Olsen, and Ted Leeson, in addition to my own experience.
So, with all that in mind, let’s walk through how to fish a pool together.
Start at the tail
It’s best to start fishing a pool from the tailout – where the pool becomes shallow and the water speeds up – up to the head. This gives your flies the most natural drift, and will usually help you avoid spooking fish.
This is a side-view diagram of what a pool looks like, and it should help you understand why we start at the tail first. Pools have a U-shape, with the deepest part of the pool usually in the middle. The head and tail of the pool are the shallowest, and where the current is moving the quickest. Starting at the tail helps you break the pool down into manageable chunks, ensuring you cover all the water and spook as few fish as possible.
This is an overhead view of the same diagram, to help give you some more context as to how pools are broken down.
Start with the risers
On any section of a pool, you want to target the rising fish first. So, if you see fish rising in the tailout, tie on a dry fly and get to work!
If fish are rising in the middle or head of the pool, don’t worry – we’ll get to them soon enough! What you don’t want is to try a longer cast to the middle of the pool, only to spook fish that were holding in the tail.
You want to cover every part of the tailout. I usually fish from left to right, but how you approach it doesn’t matter. It can be helpful to visualize a grid over the water, and you want to present your flies in each square of that grid. Speaking of flies – a dry-dropper rig is perfect for the tail of a pool because it lets you cover two parts of the water column at once. It’s also fairly easy to adjust the depth of your dropper to ensure that nymph is getting down deep enough.
As you can see in this graphic, the dry-dropper rig is covering the holding depths for the trout in the tail of the pool. This is the coverage you’re aiming for.
Finally, make sure you’re paying attention to line management. With the current picking up speed in the tailout, there can often be a few different currents moving simultaneously. That means you have to watch your drift to eliminate drag. Usually, casting across the current and making small mends to your drift is a good way to manage the multiple currents you might encounter in the tail.
Move to the middle
Once you’ve covered the tail, it’s time to move to the middle of the pool. Again, if there are fish rising, tie on a dry fly and make some casts to them. If the fish aren’t rising, then it’s time to get to work.
Devin Olsen, in his book Tactical Fly Fishing, articulates beautifully how to think about fishing the middle of a pool:
The center of a pool is a location where fish are prone to suspending in the column. Therefore, I will usually start with a dry-and-dropper rig to work from shallow to deep. Sometimes there can be several layers of fish willing to eat in a pool, and more fish will materialize as presentations work progressively deeper.
Pay attention to what Olsen says at the end – as presentations work progressively deeper. That’s key to fishing the middle of a pool. With such a slow, leisurely current, trout can hang out almost anywhere in the water column and still have easy access to food. Your first drifts through the center of the pool should focus on the higher parts of the water column, which is why Olsen recommends a dry-dropper rig.
As you can see in this diagram, we have fish holding all over the water column in the middle of this pool. The dry-dropper presents the opportunity to catch the trout highest in the water column without spooking fish holding beneath them.
Once you’ve covered that water – again, using a grid pattern is helpful to ensure you get your flies everywhere fish might be hanging out – then it’s time to go deeper. Fish can, and will, hold throughout the entirety of the water column, so you want to be thorough in the depths at which you drift your nymphs. A two-nymph rig beneath an indicator is great here, as is a Euro rig. Both allow you to easily adjust the depth of your flies and target specific areas.
After you’ve covered all the different depths, you’re ready to move on.
Stop at the top
The head of a pool usually presents the most complex currents. It’s also where you’re likely to find very active trout, since the fish here have first dibs on any food drifting down through the current.
The currents at the head of a pool are faster, as well, as you can see in this diagram:
A dry-dropper rig is what I usually stick with when fishing the head of a pool. This rig gives me better management of my drift than an indicator rig.
The head will be shallower, and this is where you’ll often see a shelf, too. Shelves are great places for trout to hide, so you want to get your flies dropping over the lip of the shelf and into the main part of the pool, to effectively mimic the real thing. That’s what this diagram illustrates:
Pools are some of the most quintessential fly fishing water, but also some of the most complex. I ruined many a good pool in my early years of fly fishing because I just didn’t know how to effectively cover all the water.
By taking a more methodical approach, you’ll be able to get your flies in front of almost every fish in a pool – and who knows? Maybe you’ll finally catch that really big trout we all know lives there.