How effective is river dry fly fishing?

Dry fly is perhaps the most enjoyable method of catching trout and grayling on a stream. It can also be highly effective. There is an often cited scientific fact that trout only take about 10% of their food on the surface and 90% beneath the surface. However this is a generalisation. At certain times most of the fish will be feeding on the surface. At other times fish are opportunists and will take a dry fly anyway. Small acidic moorland streams may be devoid of aquatic insects but support populations of small trout by surface feeding on terrestrials. A good fly fisher should never ignore dry fly as a method based on an often misused implication that more fish will be feeding on nymphs. Dry fly is extremely versatile and can be fished all over the river pool from the fast riffles at the head in the flats and slack bellies to the tails. It is a technique still widely used in competition fly fishing and I personally used it to become the English Rivers Champion in 1999.

Trout behaviour and dry fly fishing in rivers

The beauty of fishing dry fly lies in its apparent simplicity. However a good dry fly fisher really needs a good understanding of the surface feeding behaviour of trout.

The book I recommend for those interested in learning more is Vincent Marinaro's "In the Ring of the Rise". This book revolutionised my fly fishing approach by vastly increasing my knowledge of how trout saw flies and more importantly how they fed on them. I witnessed first hand Marinaro's perfect descriptions of compound rises. Where the trout drifts under the fly carefully inspecting it. This simple website is not capable of distilling Marinaro's superb observations but here is an in a "nutshell" attempt.

The rise form of a fish indicates where a trout engulfed a floating fly but not where he lies in the stream. In deeper faster water that could be several yards ahead of the rise form. A good dry fly fisher will have a good intuition of where a trout lies in relation to its rise form. It will always to some degree be upstream of the rise form. Casting flies directly at rise forms often results in failure simply because the fish didn't even see the dry fly. Not all trout rises are the same. A simple rise is where a trout lifts off the bottom and surfaces directly under the fly. But where trout are fished for on a regular basis compound or complex rises are common. In this case the trout gives the perfect impression of possessing intelligence. He rises to the fly but stops and hovers perfectly beneath it apparently inspecting it in detail. He may then either take the fly or refuse it. During this maneuver the trout may travel several yards underneath the fly and actually swivel and swim downstream (Grayling also follow flies downstream).

But before we start preparing the Diploma list for educated stream trout this behaviour can be explained by simple predator avoidance. The trout is aware that some of the flies are out to get him. He is much more likely looking for a positive trigger in the fly (something that confirms it is alive) rather than deliberately avoiding spectacular and realistic fly patterns. Marinaro knew this very well. His anecdote on the trout of the back eddy is outstanding. He confronts an old foe on a daily basis a trout living in a difficult lie in the stream rising steadily throughout the day eating humble houseflies. Everyday Marinaro casts to this uncatchable wise old fish. Everyday he tips his cap in reverence to the wise trout and goes in search of his more gullible cousins. Then one day inexplicably the trout engulfed Marinaro's house fly imitation out of the blue. In itself that might be an interesting but unremarkable story. What makes it a revelation was Marinaro's insight and observation into why the trout took the fly on that occasion after ignoring it countless times. He examined the fly and noticed the dressing had come undone and 2 strands of feather fibre were lose and blowing
against each other in the wind. It was a Eureka moment. The artificial fly was inadvertently imitating the continuous movements of the forelegs on the natural flies. That movement of the flies legs was the trigger for this trout.

The notion that trout may posses analytical intelligence can be dismissed by Marinaro's own observations. On a few occasions a trout rises to a fly and refuses it. Then after refusing the dry fly the trout appears to change his mind and go back for it. Oddly and I have observed this many times even if the fly is skating wildly and acting in a very unnatural manner the trout will attempt to engulf the fly and will often leave the water to do so. A trout that only seconds earlier was examining a dead drift dry fly like Sherlock Holmes is leaping on a fly skating wildly upstream?

This is purely behavioural and represents the yin and yang of the trout in terms of predator or prey. If we scare or spook a trout, the game is over, he will not take the fly. He thinks himself the prey and avoids the predator first and foremost. Trout that get eaten don't feed. Even if his prey senses are aroused he appears to behave very cautiously and examines the fly. He thinks better of it and refuses it. Then something clicks in the trouts mind. His predatory senses become dominant, he sweeps round and makes a beeline for the fly. Even though the fly is now behaving like no natural insect he leaps on it.

As well as these revealing insights into surface feeding behaviour of trout Marinaro looked at the world from the trouts perspective. He deduced that the first thing the trout saw of a mayfly was the tip of its wing (due to refraction of light at the water surface). I took this to heart and tied a high CDC mayfly pattern that to this day remains one of my "first on" flies on the stream. With this in mind we will examine modern dry fly variations.