Why trout take artificial flies

You cast your fly, let it sink and begin retrieving. A trout takes, and the rest is history. But why did the trout take the fly into its mouth in the first place? Anglers have pondered the question for a long time.

Why trout take artificial flies

Most exact-style fly tyers are the first to tell you that their patterns are meant for viewing only.

But if you want to catch fish it is more important to match the appropriate colour and size of the insect – as with this natural damsel fly, for example.

imitation of a natural damsel

Is this artificial an imitation of a natural damsel, or is it an attractor? The answer is probably a bit of both. The exaggerated marabou tail adds movement. Pearl or chain-link eyes make the fly look alive, and the body is ribbed to give it a segmented effect.

Fish it with short strips to imitate the swimming action of the natural.


45cm (18in) wild river brown trout

This impressive 45cm (18in) wild river brown trout fell for a dark green Cul de Canard Buzzer during a hatch of small dark olives.

Trout may reject a fly not because it didn’t look edible but because it was presented badly. “One day,” says Stan, “trout were feeding heavily on olives. I tied a brownish green imitative pattern, but it failed to catch. Later I learned that when an olive is hatching, the light shining through its body makes the fly appear golden-orange.”

Imitators and attractors

There are two general categories of artificial flies — the imitative and the attractor. The imitative pattern Most trout flies were originally designed to imitate aquatic insects, crustaceans and small fish. Notable examples are such flies as the Grenadier, Greenwell’s Glory, Black Pennell and the Muddler Minnow.

When trout are feeding selectively on a particular item, a close imitation proves most successful. Indeed, sometimes you simply can’t catch trout on anything but an imitation.

However, matching number of legs, the veining in the wings and number of body segments isn’t necessary to make a good fish-catching fly. If the fly looks good at arm’s length, it can usually be relied on to fool the most fastidious trout.

But to catch a selective-feeding trout with an imitative fly requires more than visual resemblance – you must also fish (or move) the fly in a manner that mimics the natural movement of what you are imitating. If rainbows are taking insects as they hatch in the surface film, for example, it makes no sense to present the imitative flies on a sinking line – use a floating line. The attractor pattern What of the non-imitative patterns? Such flies as Vivas, Soldier Palmers and Dunkelds are equally effective trout-catching patterns, even though they resemble nothing natural. Remember the phrase ‘take the fly into its mouth’. This, Stan believes, is the heart of the whole matter.

A trout investigates a potentially edible object by taking it into its mouth. If you watch an aquarium fish feed, it approaches a food item, visually inspects it first and then, if it looks vaguely edible, sucks it into its mouth. If the item is indeed food, that’s the last you’ll see of it. But if the fish isn’t convinced, or the item is inedible, the fish blows it out.

Though a trout may follow a fly out of curiosity, the final test of edibility takes place in the mouth, and simply because a trout takes a fly into its mouth does not prove anything other than that the fly was worth investigating.

Trout are not capable of realizing that inanimate objects can be moved by external forces. The angler moving the imitative or attractor-type fly in a likely fashion and presenting it where the trout expects to find food won’t make the fish suspicious.

Imitative flies can catch fish even when their role models are absent from the water. When trout are feeding normally – taking a wide range of food items as they come upon them — a fly which gives the impression of life and edibility is usually acceptable.

A simple solution?

Some anglers rarely use imitative flies, while others scorn attractor patterns. Both groups catch their fair share of fish. To fish both imitators and non-imitators will consistently catch trout.

But knowing just when to use imitative or attractor flies comes from experience and is something that is rather more difficult to predict – it depends on many variables such as the water you are fishing, the time of year and the weather, to name a few. Also, never forget to check the stomach contents of caught fish.