Troll Fly Fishing: What Are Trolling Flies?

Trolling flies are flies designed to attract trout in lakes at the trout’s resting depth, and to mimic the trout’s natural food sources. It is no small chore to create lures that mimic the natural food source while being pulled through the water at the end of your fishing line.

Joan Lake
Joan Lake, author of Trolling Flies articles.

How do trolling flies attract trout at their resting depth? The most important ways to attract trout are by using their own natural characteristics. What are some of these characteristics?

“The force the water exerts on the fly as it is propelled through the water changes its look, streamlines it and makes it into what a fish expects to see in deep water.”

The trout has a voracious appetite at all times. It will actively hunt or at least investigate anything that could possibly be considered prey. This is an instinct so strong that nature has taken a hand in preventing a trout from completely annihilating its natural food sources by causing its natural prey to become invisible to the trout under varying condition throughout the day. Of course this same natural phenomenon also prevents the trout from seeing the trolling fly or any other bait during these times. Many of our trolling flies take this into consideration, as you will read later in this article.

Opal Bugger Trolling Fly
Opal Bugger Trolling Fly

Another natural characteristic of the trout is its good vision; it can spot objects more than 100 feet away in clear water. This can be reduced to just a few inches when water is very murky. They have a wide field of vision and can see in all directions except straight down. This good vision enables the trout to detect prey almost instantaneously and to detect your trolling flies.

Trout can distinguish brightness and color; they have receptors in the eye similar to that in humans. Another natural phenomenon that occurs deep where fish rest, is the leaching of color due to the filtering out of light as depth becomes greater and greater. The first color that is leached out is red, then yellow, then blue. This is an extremely important characteristic to know when using trolling flies.

Lateral line nerve endings that are found along the sides of fish help them detect motion, and the speed and direction of any detected movement. This sense not only helps the fish find food, but also to escape from their predators. This sense is not too important in the design of the trolling fly itself but it is important in the use of spinner attachments that may be used with trolling flies.

Two Wooly Muddler Trolling Flies
Two Wooly Muddler Trolling Flies

Another way that trolling flies attract trout is by mimicking the natural food source of the trout. They do not mimic it by becoming exact replicas of the food source you see in dry fly fishing, but by approximating the look of the natural prey. This is fortunate because a nymph pattern, which has a long, slightly slender body with a short hackle at the head to signify legs, can mimic a multitude of the hatching nymphs of may, damsel, dragon and stoneflies. The approximation of the leech and woolly patterns are just as effective.

The reason these flies do not need to closely resemble the look of the original prey is because of the movement of the fly while trolling. The force the water exerts on the fly as it is propelled through the water changes its look, streamlines it and makes it into what a fish expects to see in deep water.

Many trolling flies look slightly messy out of the water. The hackle of leech and woolly patterns is long and thick as it tries to give more substance and density to these flies. You will see a lot of chenille used on trolling flies. Chenille is important because it absorbs a lot of water and cause the fly to be heavy and balanced. The heavy fly will present to the trout on a straight plane, which is what the trout expects to see in deep water.

Color is one of the more important design features of the trolling fly. The brightness of the fluorescent colors, such as fluorescent orange, fluorescent green, and fluorescent pink will remain visible to the fish when other colors are rendered invisible by natural light changes and become visible again sooner than other colors when the light again allows prey to be seen by the trout. This gives the fish a greater window of opportunity to feed than natural conditions allow.

The natural leaching of color that occurs as the fly is presented deep is a decided challenge to the fisherperson. What we see when we choose colors for flies is not exactly what we get when it is presented to the fish. The fish however does know what it likes, so it is worth the effort and money to keep a multitude of colors and patterns in your box, and keep trying them until the trout tells you what is popular that particular day.

About Joan Lake

Joan Lake, of Republic, Washington, has been creating and selling trolling-flies since 1990. She started and previously owned Lake Trolling Flies Web site at


“What are Trolling Flies?” article contributed by Joan Lake on  October 9, 2004. Reprinted by permission. Trolling flies photos taken with Joan Lake’s permission from