Fly Fishing

Where Do Trout Lie? Reading The Water

Understanding where trout lie and why they lie in certain parts of a river can ensure the majority of an anglers time on the water is spent fishing water that is likely to hold trout rather than wasting time in areas that aren’t particularly attractive in the mind of a trout.

Trout aren’t swimming around deciding where to lie at random. They are smart and have criteria that spots need to meet. Any spot that a trout decides to spend a significant amount of time in needs to meet this criteria… As such you, the angler, should be asking yourself these questions when considering where to spend your time when exploring new water.

Does this piece of water have a continuous and plentiful source of food?

A trout’s food source is made up of a few things. Invertebrate nymphs, floating insects and other smaller fish are the three main food sources for most species of trout. 

Given this, it is logical that a trout will spend the majority of its time where it has access to these food sources, floating insects and smaller fish provide somewhat opportunistic food sources that may depend on time of year. However, invertebrates/nymphs are present all year round and are said to make up about 80% of a trouts food source. This being the case it is important to look for water that will have a concentration of any organic matter flowing downstream. Look for these things as an indicator of where most of the organic matter may be concentrating:

  • Foam Lines – Foam lines are where they are for a reason, any foam that has been stirred up is concentrating on the surface. Organic matter above and below water is being drawn to this piece of water as a result of surrounding currents.
  • Current Seams – Current seams are where two pieces of water of different speeds meet. In effect, this creates a feeding lane where more food will be found due to the converging of currents (and the organic matter the current holds).
  • Eddies – An Eddy is a piece of water next to the main current that recirculates and travels back around in the opposite direction. Due to this reverse flow trap, a lot of organic matter from the river often ends up circulating in an eddy before it is eventually ‘spat out’ back into the main river current. Fish will often lie in the eddy or in the seam between the main flow between the currents.
Illustration of flow features creating feeding channels

Does this piece of water provide trout with oxygenated water?

Like every living animal trout need oxygen to survive. Trout will seek out highly oxygenated water as an ideal place to lie. River water is oxygenated as it is exposed to air through riffles and rapids. Trout will seek oxygenated water especially during summer (warmer water holds less oxygen than cold water). Expect to see or find trout gathering in riffles or at the head of a pool in search of this oxygenated water.

Can a trout lie here without using an unnecessary amount of energy?

This goes hand in hand with seeking out a spot with a good food source. Trout rely on high numbers of low-calorie meals for energy, given that food sources aren’t always plentiful a trout is not going to then spend its time in a lie of raging water only to expend all the energy and calories it has worked hard for. Trout will seek out spots that strike a balance of food source (which in a river requires some current) and energy conservation. If a trout can find water with a reliable food source where it does not have to exert large amounts of energy, that trout will obviously grow bigger and stronger.

Trout will often park themselves behind a large rock or some other kind of structure that creates a pocket of softer water (as seen in the above diagram). This is especially ideal in swifter currents as the surrounding fast current presents a good source of food while the trout sits in a pocket created by a large boulder. Food also is swept into the pocket for the trout in a similar way which it does with an eddy.

Does this piece of water provide shelter?

The three requirements above of food, oxygen and ideal current are the essentials. 

This fourth requirement of shelter is somewhat of a luxury and isn’t always possible especially in smaller, bouldery rivers. However shelter often presents itself as overhanging trees, logs, deeper water and undercut banks. As shelter can be scarce and there is often more trout than well sheltered lies it is often reserved for larger fish who have the size and wits to bully smaller fish for prime position. How many times have you seen a trophy trout lying under an overhanging tree or shrub requiring a near impossible cast to reach and you just think to yourself “of course you are”.  

Wrap Up

Keeping these questions in the back of your mind as you explore new water is a good way to ensure your fishing water that is seen as habitable in the mind of a trout. This way you are able to spend your time on the water casting to water that is likely holding fish rather than thrashing away in a spot that most trout would pass on.

Happy Fishing!

Leave a Reply

%d bloggers like this: