Reading Water and Finding Trout in Rivers

Reading Water and Finding Trout in Rivers

There is a short period of time that I specifically attribute to the confidence I now have as a fly angler. After years of trial and error, sporadic success, and countless hours spent casting and researching trout behavior, my level of success and consistency improved drastically over the course of just a couple of weeks. Until that point most of my attention had been focused on fly selection and achieving a proper drift in what I viewed as good trout water. I began to focus almost exclusively on fishing every part of a river, exploring each feature in a way I had not considered before. This revealed a great number of trout in what I previously viewed as unassuming areas.

Many new anglers are overcome with the emphasis on fly selection and river conditions that they’re confronted with every time they walk into a shop. With all of the talk about bugs and which rivers to fish, it is easy to overlook the importance of fishing the structures and currents that most frequently hold fish, regardless of river or geographic location. It can be difficult to gain a sense of how to properly read water without firsthand experience on the river, so it is important to actively choose the structure fished on each outing. Fortunately, we are able to use images and detailed descriptions to provide general direction and characteristics to look for and focus on the next time you hit the water.

There seems to be a common misconception that the deepest, oftentimes slowest moving holes in a river are the best place to fish. There is no doubt that the large deep holes typically do hold large numbers and large sized fish, but a focus on this type of water puts up blinders to the more common structures that hold trout in nearly any stretch of water. The reality is that trout will consistently feed in just about any area, so long as a few basic habitat characteristics are present.


River dwelling trout are very well adapted to feeding efficiently, in a way that harnesses the energy of the environment in which they live. Essentially the current of the water allows trout to hold themselves stationary, expending little energy as the river carries aquatic insects, eggs, and leeches directly to them. This current is very important to the feeding habits of trout in almost all river environments, and is necessary (with very few exceptions) to consistently finding fish.


With any sort of current, we will obviously see disruptions and changes in the direction, speed, and depth of the water as it moves around various structures. Whether a large rock, fallen tree, undercut bank, or gravel bar, different features within a river dictate the way in which the water moves downstream. These structures are important to us as anglers because they disturb the consistent flow, concentrating food sources and fish in specific areas that provide shelter from the brunt of the main current. Structure and the dynamic aquatic environment that it creates are at the center of reading water and identifying fish habitat.


Of course fish will need to be feeding if we hope to catch them consistently, which necessarily requires a food source. The most consistent and abundant source of food for trout in streams are the aquatic insects that we all spend so much time discussing in fly shops. Caddis, Mayflies, Stoneflies, Midges, and all variations are potential food sources among others. Typically these insects develop and live in the substrate before rising to the surface to emerge as adults. These insects are vulnerable to trout as they move towards the surface or when they are swept from their rocky realms at the bottom of the river. There are certain characteristics in terms of water speed, water temperature, and riverbed composition that lend themselves to specific species of insects, which can help us direct our efforts when we are looking for trout. We’ll dive deeper into insect habits and descriptions in a future post.


A characteristic that is not to be overlooked is the water’s oxygen level. Trout are creatures adapted to cold, clean, highly oxygenated waters, and struggle in areas of warm or stagnant water with low oxygen content. Many variables can impact the level of oxygen in an area, including but not limited to time of year, water temperature, and water speed/aeration. There are times throughout the year in which different features within the same stretch of river will have desirable oxygen content, which can help us focus further on the areas in which fish are likely to be concentrated.

With these necessities in mind, we can now look at the structure types that consistently hold feeding trout.

Seams/Converging Currents

Any place at which multiple currents come together in a “seam” is a natural concentration point for insects and debris being carried downstream. These convergences are often turbulent, with currents of multiple speeds in close proximity to one another, and can be difficult to fish well. However, they are natural holding areas for feeding trout, which take advantage of the varying currents to hold and rest in the slower water while moving slightly to feed on passing insects as they come by in faster currents. These areas can be deep, allowing fish to stay comfortable and cool as they feed throughout the day. The largest challenge to fishing seams is in managing line so that flies move as naturally as possible, particularly when they are under an indicator and move differently than what is shown on the surface.

The image above illustrates several seams that could potentially hold trout. These eddylines and channels of soft water provide areas for trout to rest while maintaining access to a consistent flow of food.

Pocket Water

Pocket water is a favorite for many fly anglers, and is common on small-medium freestone rivers and streams throughout the West. Pocket water is typically characterized by a streambed comprised of rocks and boulders of various sizes. The large rocks that displace the most water leave “pockets” of eddying current that offer slow holding water and shelter for trout. Pocket water is some of the easiest water to read, and the sheltered areas of current which hold trout are typically quite obvious. It can be very satisfying to work through a stretch of pocket water, placing accurate casts and plucking fish from nearly every suspected holding area. It’s possible to find fish in surprisingly fast, shallow, and tiny pockets, which can reveal a lot about the character of the river and the fish it supports.

Multiple rocks create “pockets” that are likely to hold trout. The seams on the outside edges of the rocks and soft areas directly downstream should both be fished when searching for feeding trout.


Riffles are another favorite of many anglers. These unassuming fast and sometimes shallow sections of water can produce surprising numbers and size of fish throughout the summer. Warming summer water temperatures allow fish to expend the energy necessary to hold in these riffles, which can hold great numbers of Stoneflies and Caddis. As waters continue to warm and oxygen levels decrease the highly aerated riffles and waters directly downstream of them can hold great numbers of fish, especially in the evenings or anytime the sun is off the water. Dries, nymphs, and streamers can all work well in riffles depending on conditions. We always like to let our flies swing in hopes of reactionary strikes from unsuspecting fish.

Griff shortly after finding a Redband in a Lower Deschutes riffle. These large, open gravel bars and riffles are common on large Western rivers. While the sheer size of potential holding water can be intimidating at first, many anglers find success by fishing the soft edges and inside portions of the big runs, where achieving a good drift is manageable.

Deep Holes/Runs

The deepest parts of a river are some of the most classic and easily identifiable holding water. We like to fish areas with relatively steady current, ideally with submerged structure which may or may not be visible. These areas are comfortable strongholds in which fish can feed and rest without worry of danger from above and away from the sun during the brightest parts of the day. While these areas can be some of the most consistent to fish day in and day out, they often require more time and searching to find the subsurface structures and currents that hold the greatest numbers of fish.

Above we see a classic deep hole with various holding areas for trout. Towards the head of the pool, there are two defined channels with consistent current dumping into deep water. Through the rest of the pool, we see a multitude of submerged rocks and ledges that provide an excellent structure for feeding or resting fish.

Transition Areas

As a general rule, areas of transitioning depth or current speed offer excellent holding water for trout. Many of the structures we’ve described above include transitions of some sort; whether the transitioning currents in a pocket behind a boulder or the dropping gravel bar of a productive riffle. Heads and tails of deeper runs, where faster current pours down and in or is funneled up and out are great places to find fish. Shelves or river bends that have a deep channel on one side and shallow rock on the other are also places to look for. The areas of transition often hold feeding fish in a more concentrated manner than the big, deep areas that always look enticing.

The photo above shows a deep channel that offers obvious habitat for trout. Both the ledgy transition on the inside of the bend and more gradual transition on the outside of the bend have the potential of holding feeding fish. I love fishing the gradual transitions and finding fish at various depths as I work the flies farther towards the center of the channel with each drift.


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