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Reading the Water for Fly Fishing

Locations that will deliver in creeks, rivers, streams, lakes, and ponds.

Reading the Water for Fly Fishing

(This story appeared in the 2019 Fly Fishing Made Easy issue of Fly Fisherman and was originally titled "Reading the Water: Twelve Locations That Will Deliver in Creeks, Rivers, and Streams.)

Locating fish is the first step to a successful outing. In moving water, predatory fish hold in the same types of places, whether they are trout or smallmouth bass. Fish in streams and rivers have two primary survival motives: 1 ) Finding shelter from the current and from predators; and 2 ) maximizing feeding opportunities.

Generally, there is more food in faster current because, like a conveyor belt, faster current moves more food toward the stationary feeding fish. However, trout, bass, and other predators must expend more energy in fast current, and if there’s not much drifting or swimming food, the effort may not be worthwhile.

In addition to shelter from the current (and access to food), bass and trout require protection from predators such as otters, ospreys and other birds of prey, wading birds such as herons, and humans. Large bass and trout are often conditioned to hold in places that are difficult to reach—under an undercut bank, under a weed mat, under an overhanging tree branch, at the bottom of a deep hole, or behind a rock in fast water. All these places offer both feeding opportunities and shelter from predators.

Because of this constant balancing act, the most logical and obvious places to start looking for trout in moving water are areas where there is a current change—places where trout can sit in slower water, yet have close access to faster water, where they can dart out, grab a food item, and return to their holding spot.

Reading the Water for Fly Fishing
(Dave Hall illustration)

Be aware that these holding spots are not equally productive at all times of the day and in all seasons. A shallow flat that is barren all day may be a hunting ground for large browns at night when darkness provides the “protection from predators” condition.

Cold water lowers fish metabolism, causing them to feed less and seek water where they expend less energy, therefore favored wintering holes are slow and deep.

In the spring when water temperatures rise, fish feed heavily and move into areas with better access to food. When summer water temperatures rise into the 60s and higher, the oxygen content of the water becomes a factor, and trout move into the riffles and fast water where there is plenty of food and the water is well oxygenated.

Here is a short list of the best spots to find trout and bass:

UNDERCUT BANKS. A stream or river erodes softer soil layers while the hard-packed top layers—often held together by grass, roots, or other vegetation—remain intact. The result is an undercut bank: a trout hotel favored by big fish. They hide from the sun and overhead predators and occasionally dart out into the current to grab grasshoppers, stonefly nymphs, or prey fish.

It’s difficult to get at these fish from directly above since when you walk on the undercut bank, fish can detect your footstep vibrations, and they may spook or develop lockjaw. The best way to present a fly to fish holding under an undercut bank is to wade from the opposite shore or, in a larger river, to drift in a boat and cast as close to the undercut as possible.

Whether you are fishing nymphs or streamers, try not to retrieve the fly away from the undercut too quickly. Dead-drift the fly alongside the undercut, or retrieve it upstream or downstream parallel to the undercut to expose the fly to as much of the undercut for as long as possible. You don’t know exactly where the big trout are holding, and sometimes an undercut can run for a hundred feet or more.


OVERHANGING VEGETATION. Overhanging tree branches and shrubs provide cover from airborne predators and, as a bonus, they frequently drop terrestrials such as ants, beetles, and inchworms into the water, so consider using these types of fly patterns. If the branches are over the water—but not in the water—it’s often possible to cast a dry fly upstream and drift it right under the branches. You can also do this with wet flies such as nymphs and streamerscast upstream of the tree limbs, and drift the fly under the branches where you suspect the fish may be holding.

If the branches are dragging in the water, getting your flies to the fish is more difficult. Dry flies usually won’t work unless you approach from downstream and cast as closely behind the branches as possible. Sometimes you can still drift wet flies under the dragging limbs, especially if they are only partially submerged and you cast well upstream, allowing plenty of time for the flies to sink.

BACKEDDY. The current in a backeddy is circular. Near shore, the current often moves in the opposite direction of the main current, and fish facing into the current are facing the “wrong” direction in relation to the rest of the fish in the river. It can be difficult to get a dead-drift in a circular backeddy, but the rewards are great: Backeddies can hold enormous numbers of fish, especially in fertile spring creeks and large tailwaters.

Reading the Water for Fly Fishing
Side sloughs, lagoons, and backeddies that are connected to the river collect food, and provide refuge from the current. (Cathy & Barry Beck photo)

BEHIND A ROCK. A large midstream boulder is a frequent feeding spot for trout because the rock provides a strong current flowing from both sides, and a sheltered spot to sit and watch for food.

To catch trout directly behind the rock, cast your fly upstream of the rock and allow it to drift in the current to one side of the rock or the other just as a natural food item would.

Sometimes trout hold well downstream of the rock. In these cases you can cast behind the rock and drift your flies down the current seam until the seam disappears.

IN FRONT OF A ROCK. When flowing water hits the front of a rock it pauses for an instant before the water pushing from behind forces it to flow around the rock. This dead zone—often described by angling writers as a “pillow” or “cushion” of water—is an easy spot for fish to sit and wait for food. It is less turbulent, so it’s both easier for the trout to see food drifting toward it, and easier for you to spot the fish if the water is clear and shallow enough.

The spot in front of a rock is not a great “holding” spot like a deep pool or even behind a rock. This position is generally used only by fish that are actively feeding. Approach carefully from below and slightly to the side so the fish can’t see you. Cast upstream of the rock and allow the fly to dead-drift directly toward the fish. To avoid snagging the rock and losing your opportunity, begin with dry flies and then switch to lightly weighted emergers and nymphs before trying more heavily weighted nymphs or streamers.

CURRENT SEAMS. Wherever a tributary or side channel enters a main river; where two currents meet below a rock, gravel bar, or island; or where the current tumbles around an obstruction along the riverbank, there is a current seam where two opposing currents collide or where fast current meets slower current.

Trout and bass sit along these seams, using the break in the current to avoid expending energy, yet using the nearby current to bring them food. To catch these fish, your flies should drift directly down the seam like a natural food item.

HEAD OF A POOL. A pool is a wider area of a stream or river where the water is also generally deeper and slower. By definition, the area above the pool is constricted in some way—either by a narrow stream channel, a shallow riffle, or even a small waterfall. Where this constriction loosens is the head of the pool and it’s a major break in both the current speed and depth.

Reading the Water for Fly Fishing
In small mountain streams, the head of a pool is often a plunge pool where a shallow riffle or small waterfall creates an obstruction with a deep holding/feeding spot below. (Ross Purnell photo)

Fish gather at the head of the pool to feed on the food pouring in from the riffle or faster water upstream. In small mountain streams, the head of a pool is often a plunge pool, where water falls over boulders into deeper water below. Trout pick out these areas as both prime feeding and holding spots.

TAIL OF A POOL. The gut of a pool— the deep, dark area in the middle—is a fine place for fish to hide and rest. When they decide to feed, they move to the head of the pool (see above) or drop to the tail of the pool where the water speeds up and is shallower.

When there is a hatch, the shallow tail of the pool can provide excellent fishing because the trout remain on the bottom and still have easy access to the hatching insects drifting overhead. However, the tail of a pool can be a tricky place to get a drag-free drift because you often approach from below, stand in a fast riffle, and cast upstream into much slower water at the tail of the pool. The fast water in the riffle pulls on the line, and can cause dramatic drag if you don’t get enough slack into the line.

TRIBUTARY. Small streams entering the main river can bring cooler water and additional food sources. They can also produce a current seam fish use to feed. Pay particular attention to these places in the summer when the main river warms and fish gather near the cool inflows. Avoid these places in the spring or after heavy rain when they flood with muddy water.

BANK OBSTRUCTIONS. When you drift down a big river in a drift boat, you often “pound the banks” with streamers, nymphs, or big dry flies. While many new fly fishers tend to wade too deeply and focus on the middle of the river, expert anglers know that on big rivers especially, trout avoid the heavy current in the center of the river and use obstructions along the bank to give them both relief from the current and excellent feeding opportunities.

Reading the Water for Fly Fishing
On large rivers especially, look for trout to hold in sheltered areas along the bank such as behind wing dams, boulders, logs, clumps of sod, or other obstructions. (Ross Purnell photo)

Fallen clumps of grass and soil, downed logs, streamside rocks and boulders, irregularities in the bank, fences in the river, bridge abutments, wing dams, riprap, and other obstructions along the bank all create breaks in the current, and as a result, current seams where fish hold.

DEPTH CHANGES. Knowing the contours of a river bottom can help you catch more fish. When the water is low and clear, pay attention to the potholes, depressions, and gravel bars that form the terrain of the river bottom.

Reading the Water for Fly Fishing
Changes in depth that constitute potholes, depressions, and deeper slots along the bottom create ideal holding water for trout. (Cathy & Barry Beck photo)

When the water is higher or off-colored, you can use this information to catch fish lying in the deeper spots, feeding on food items passing overhead. Remember that the water on top of the river travels much faster than the water on the bottom, and the water in depressions along the bottom can be nearly motionless, while faster water rushes past overhead.

RIFFLES. Fish in the riffles are hungry. They aren’t there to rest or avoid predators, they are there to feed, and because food drifts past quickly, they have little time to inspect and consider your fly when it drifts past them. Relative to fish in flat, slow water, trout and bass in the riffles are easy to catch. In the riffles, use large, heavily hackled and/or foam dry flies that are extremely buoyant and easy for the trout to pick out and attack.

The bumpy water on the surface of the riffle is caused by numerous rocks and gravel undulations along the bottom. While riffle water might seem fast, obstructions create a slow zone on the bottom. If you are using nymphs, make sure you use enough weight—usually split-shot—to sink the flies quickly and drift them slowly along the river bottom. Your flies should travel slower than the surface currents, therefore your indicator—if you are using one—should actually appear to be dragging to indicate that your nymphs are moving slowly.

When you are streamer fishing, the turbulence of the water adds all the movement you need. Because of the erratic current in a riffle, trout sometimes have trouble tracking and eating the fly, and may not bother to chase a food item that appears to be swimming too quickly or strongly. Move the fly slowly (from your vantage point) and keep a tight line so that you don’t miss the strike.

Where to Find Fish in Stillwaters

In a stream, trout are relatively stationary–they find shelter from the current and sit in one position waiting for food to come to them. In lakes, ponds, and reservoirs, trout are constantly on the move, both to find food and keep oxygenated water flowing over their gills.

Stillwater trout do not roam the entire acreage of a lake. They are attracted to food-rich areas to maximize their feeding opportunities and–depending on the season, temperature, and size and depth of the lake–they also collect in the lake strata that are most comfortable for them.

Trout prefer water temperatures between about 55 to 60 degrees F. Brown trout tolerate (and even seek out) slightly warmer temperatures, while brook trout and cutthroat trout do best in cooler temperatures.

Lakes with frequent water temperatures of 70 degrees and above are warmwater lakes, and are most likely home to bass, panfish, and other species.

Deep lakes. In shallow lakes the water temperature is fairly constant throughout the water column. However, in deep lakes and reservoirs, the surface temperature can be intolerably warm for trout while the water temperature 40 feet below the surface is perfect.

This is because cold water is denser than warm water and stays near the bottom, and because the radiant heating effect of the sun only affects the surface layers. This stratification results in layers of water, with the warmer layers generally on top and the coldest layers toward the bottom.

If you are fishing a deep lake with stratified water temperatures, finding the fish becomes a depth game. You'll need a boat, float tube, or pontoon craft to get out over deep water, and a full-sinking line, or a floating line with a long leader and strike indicator to get your weighted nymph or streamer down to where the trout are.

With sinking lines use the countdown method: Cast as far as you need to reach the bottom and then count "one one-thousand, two two-thousand, three three-thousand" and so on to allow the fly time to sink deep to the colder lake levels where the trout are. Retrieve your fly slowly so the fly travels horizontally through a specific depth, and doesn't rise quickly toward the surface.

Begin with a count to ten, use that for 15 minutes or so, then graduate to a count of 15, and so on. Once you find where the trout are, you can reliably count down to the same depth to catch many more.

Another way to find the bottom quickly, and adjust your fly depth accordingly, is with the help of an electronic depth finder, which also gives water temperature information.

To determine the depth without a depth finder, attach hemostats to your fly and leader and drop the rig off the side of your boat or pontoon. Strip off line until you hit bottom, then mark the depth. With precise knowledge of depth, you can start at bottom and fish your way up through the water column until you find the level at which the fish are feeding.

In shallower lakes and ponds, the temperature is relatively constant, and trout focus on specific feeding opportunities more than water temperatures. In high mountain lakes, the "warm" shallow edges of a lake may never rise above 50 degrees F.

On big lakes in the late fall, winter, and spring, the deepest parts of the lake are often too cold, causing the trout to venture into the shallows during the day to find food. These are the best seasons and situations to pursue trout in stillwaters because the fish are in their comfort zone, feeding happily at depths that are best suited for a fly rod and floating line.

INFLOW. If it is hot outside, fish gather near inflows because feeder streams often bring cooler, or at least more oxygenated, water into a lake. Even when there is no temperature advantage to the inflow, the current sweeps food into the lake.

Use stream tactics such as a nymph and indicator rig to drift your flies from the stream into the lake. Pay particular attention to the area where the stream shallows drop off into the depths of the lake, as fish tend to cruise there in search of easy meals.

OUTFLOW. An outflow doesn't bring food into a lake, but it's a shallower area with a gradually increasing current where the lake falls away into a stream. Trout take advantage of the current: They sit in the moving water and watch for food items like midges, mayflies, and terrestrials drifting toward them.

An advantage for fly fishers is that the area where the current quickens is by nature shallower than the rest of the lake and affords more opportunities for sight fishing. Approach these areas slowly and with a low profile, watching carefully for feeding trout. As with an inflow, don't cast directly to a stationary trout or you may spook it. Use the current or wind drift to bring your fly to the fish.

SHORE AND SHALLOWS. In big, deep lakes in warm climates, trout are often deep and difficult to reach. In small alpine lakes, the deepest part of the lake is a winter refuge only. When the trout feed, they seek out the shoreline and shallow flats where the sun penetrates to bottom and stimulates the food chain.

The shore is also a constant food source for trout where ants, beetles, and other terrestrial insects fall or blow into the lake from nearby vegetation, or where insects like damselflies migrate from the lake depths to the shoreline to hatch.

The best strategy is to approach the shore cautiously wearing polarized glasses and a baseball cap to block glare. In lakes with good trout populations, you'll see trout cruising the shallows.

Try to predict the path of the moving trout and cast your fly well in front so you do not alarm it. Allow the trout to spot your fly and then race toward it. It's one of the most exciting ways to hunt stillwater trout.

If wind is causing waves on the water, seek out the leeward end of the lake (the end the wind and waves are blowing toward). Wind and waves often accumulate surface foods along the shore on one end, and the fish recognize these situations. You may have to cast against the wind if you're fishing from shore, but the fish will be close, less spooky because of the wave action, and preoccupied with feeding.

SUBMERGED LOGS. Trout in shallow water often maintain and patrol a well-defined territory, and these areas are often near or around a downed tree, boulder garden, rocky outcropping, shelf, or other type of structure. If the water is clear and shallow, study these areas closely from a high vantage point before you cast.

One reason trout prefer these areas is because they offer extra security from predators. Logs, rocks, and underwater shelves provide places to hide and may obstruct your view of the bottom, so sightfishing may not be possible. Use shallow-swimming flies such as Callibaetis nymphs, damselfly nymphs, and Woolly Buggers, and swim them slowly above and around the structure to entice a predatory strike.

OVERHANGING TREES. Overhanging tree limbs provide shade, protection from airborne predators, and are a constant source of terrestrial insects such as caterpillars, inchworms, ants, and beetles. Keep your casts low to the water so you can get under the overhanging limbs and present your fly as if it fell from the tree. Sometimes an audible "plop" acts as a dinner bell for less wary wilderness trout. At other times, you must land your fly softly.

After the fly lands, allow your terrestrial imitation to sit motionless for an extended period. Then try twitching the fly subtly, as if the insect was twitching its legs, attempting to crawl across the surface meniscus, or take flight. Sometimes the slightest movement can be an incentive to strike.

SPRINGS. Coldwater springs entering the lake as tributary streams or welling up from the bottom are critical feeding areas. Use a thermometer or look for clear sandy or rocky areas on an otherwise weedy lake bottom to find these areas.

Stream channels. In shallow lakes or reservoirs, look for submerged former stream channels or possible pathways between heavily weeded areas. Trout use these underwater highways to move from one feeding area to the next. Sometimes the channels are the feeding areas, since the rest of the lake is too choked with weeds for the fish to feed comfortably.

On Henry's Lake, Idaho, for example "The Ditch" extending from Staley Springs is one of the best fishing locations–especially in late summer when water temperatures are high and weed growth is at its heaviest. The spring brings cooler water into the lake, and large trout prowl up and down The Ditch looking for food.

WEED BEDS. Aquatic vegetation is the base of the food chain that grows trout foods. Weed beds are full of damselflies, scuds, daphnia, Callibaetis nymphs, leeches, and snails, so concentrate on imitating these food items.

If the weed bed reaches the lake surface, fish around and near it. Position your boat or inflatable so you can cast parallel to the weed bed, and retrieve your fly along the weeds for as long as possible.

Often the weeds do not quite reach the surface, creating a shallow-water fishing situation where trout cruise just above the weeds, picking off both surface foods and food hiding in or ascending from the weed bed. Use a floating or clear, intermediate sinking line and retrieve your fly slowly, just above the weeds.

Float Tube Tactics

In a boat, pontoon, or float tube, you can cover much more water than wading the shoreline on foot. This is a big advantage, especially on featureless lakes in the spring, when the weeds have not grown up, and terrestrial insects are not yet important.

One of the easiest ways to get started fishing stillwaters is to slowly troll a Woolly Bugger or Zonker from a float tube or inflatable pontoon boat. You don't even need to cast, just move your tube over water 5 to 10 feet deep, start slowly kicking your fins, and pull line from your reel, allowing the fly to trail behind you by about 60 to 90 feet.

Each time you kick your fins, the fly pulses and swims forward, and then it hesitates and drops while your legs scissor for the next kick. Keep your rod tip low while you troll so you can effectively raise it to set the hook.

Chironomids. The most important aquatic insects on many stillwaters are midges, members of the Chironomidae family. Midge ­larvae live in the mud at the bottom of both stillwaters and streams. In lakes, they are incredibly abundant, and the individual insects are much larger than the midges normally found in streams and rivers. Stream midges are regularly imitated with #16-28 hooks, while midge pupae in lakes fall into the #8-16 size range. (See "What Trout Eat" for complete information on the midge life cycle.)

Trout root on the bottom for midge larvae, and they also eat adult midges on the surface, but the most important and dependable phase for fly fishers is when midge pupae leave their burrows on the bottom and travel to the surface to hatch. Trout cruise near the bottom looking for these midge pupae and in some cases they chase chironomid pupae as they ascend toward the surface.

Since pupae travel upward from bottom to top, it's important that your imitation does the same. To mimic this behavior, use a strike indicator and a monofilament leader up to 20 feet long, depending on the depth of the lake.

Your leader length–the distance between your fly and the indicator–should be only slightly shorter than the depth of the water so you can suspend your fly just above the bottom. Attach one or two split-shot 12 to 18 inches above the fly and allow the fly and weight to sink and then hang vertically below the indicator.

The indicator acts as a float that suspends your fly just above the bottom, or at varying depth levels depending on where you find feeding fish. Test the bottom with midge larva imitations, and work your way up through the water column with various ascending pupa imitations until you find what works. With a little patience, you will find the best combination of depth and pattern, and the trout will reward your efforts. If your fly snags the bottom, shorten the leader. Lengthen the leader if you suspect the fly is not close enough to the bottom. When you slowly retrieve the fly and indicator rig, the fly moves horizontally near the bottom, imitating a highly vulnerable life stage and keeping the fly in the most likely strike zone.

Midges begin hatching just days after ice-out and continue hatching on many lakes–depending on elevation–until late July. The most intense hatches occur in the spring when water temperatures near the bottom reach between 50 and 55 degrees F. This occurs early in the season in shallow water warmed by the sun, and in late spring or early summer in water 20 feet deep or more. Knowing the bottom contours and depth of your favorite lake helps you predict where and when the most concentrated midge hatches might occur.

Midges are most often black, olive, maroon, red, dark brown, or even pure chrome, and their bodies are heavily segmented. Midge pupae also have cheeks and gills, both easily imitated with a white or colored beadhead and tuft of white Antron or CDC near the hook eye.

At certain times and locations, most midges are predominantly one color. Sometimes trout key on more than just size and shape and show a preference for a specific color.

Use an aquarium net to take midge samples from just under the surface, and match your imitation to the most prevalent size and color. You don't need many different types of patterns. The Black Beauty or the Jujubee Midge cover most situations, but you'll need them in sizes 10 through 16 and in several different colors.

Ross Purnell is the publisher/editor of Fly Fisherman.

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