Salomone: Microstructure

The river has been slowly waning until recent rains spiked river levels and muddied up the lower Eagle River. The slowly receding water level illustrated how important microstructure is to fly anglers. A broad stroke approach is often applied when fly fishers hit the river. But the attentive wading angler finds increased success when they concentrate on breaking down a stretch of river into smaller, river formations. Concentrating on the key components during low water steers anglers toward a focus on microstructure.

In a normal stretch of river, anglers will encounter a variety of conditions. Dissecting the river helps anglers to choose a productive approach to fishing a specific piece of structure whether its deep water, riffles, pocket water or a boulder field. Pairing up a specific fly-fishing technique sets anglers up to concentrate on similar conditions as you wade through a stretch.

As water levels drop, small variations in river depth become more important. When the river was flowing around 800 cubic feet per second (CFS) at the beginning of July, shallow boulder fields were covered with a few feet of water. Up until a few days ago, diminished levels had uncovered boulders, thinned water depths and created small places where fish concentrate.

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Impressions in the river bottom that may only drop 6, 8 or 10 inches are irrelevant when CFSs are high. But when we begin to feel the effects of lower water levels and decreased CFSs, those shallow depth-changes possess the ability to hold fish. This is one example of microstructure.

Dry-fly anglers will primarily fish pocket water or shallow riffles. Lower water levels make each boulder a piece of microstructure. The cushion on the front of the rock, another example of microstructure, is a feeding position that deserves focused attention. Trout surf the push, surveying the conveyor belt of food as it approaches.

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The eddy behind a boulder is always a targeted area dry-fly anglers pick apart. River current will scour out the pocket behind a boulder. This creates a resting area where trout can grab food from the current as it passes beside the rock and immediately reposition back behind the current-breaking boulder. This type of microstructure deserves an extended amount of attention. Depending on the depth, anglers can fish this pocket first with a dry fly, then with a dry dropper and again with a shallow-water nymph rig.

Wading anglers have the benefit of a slow, more focused approach to microstructure. Anglers wading can present their flies repeatedly to one piece of microstructure as opposed to float fishers that usually get a one and done shot at structure.

Shallow riffles are faster sections, but they hold underwater structure that is very difficult to discern. Fish actively feeding in shallow riffles will rise to a well managed dry fly, eat a dropper nymph following a larger dry fly or even feed on a shallow water nymph rig. The riffle becomes the microstructure that the fly angler wants to focus attention on, rather than a piece of concrete structure like a boulder or log. The moving water in the shallow riffle creates a unique sinuous situation that can produce high numbers of fish.

Breaking the river down into manageable pieces of smaller structure and dedicating a focused approach to each piece will maximize angler success. A shallow-water nymph rig is a finesse nymphing approach that can be superbly productive as water levels diminish.

A pair of nymphs tied in tandem and set no more than a few feet deep is an effective way to present subsurface insects to any type of microstructure. Strike indicators need to be light and responsive. A fish that feeds in a shallow riffle may spin a single indicator rather than submerging the tool. This is a very difficult bite to detect. The shallow water angler that utilizes a pair of pinch on strike indicators, however, detects the slightest movement.

The pair of indicators will spin and change their relationship, indicating an eat. Foam, pinch-on, palsa-style indicators are easy to cast as well.  

Pick every piece of microstructure apart with well-placed casting. Proper mending is the key to selling it no matter what approach an angler chooses. Dry-fly, dry-dropper or shallow-water nymph fishing all allow the fly fisher to dissect the river for maximum success. Having the ability to select productive microstructure as the water level drops will enhance your angling experience.