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Choosing a Successful Fly

Tony E

15 May 2023

Getting Down to Basics is the Key.


Building up a fly box of patterns that you have confidence in is fundamental to becoming a successful fly-angler. One of the most common questions I am asked about fly fishing is, “What is the best fly to use?”

Selecting an effective fly can be a confusing struggle given the vast range of patterns available. It helps to recognise the various insects that trout feed on, by either checking the surface of the water, the air above or under the stones beneath, but names of the different species are mostly irrelevant. Getting down to basics is the key. There are only a small number of variables in the makeup of a fly.

When selecting dry flies the principal keys are shape, size, profile and colour, while nymphs have the additional variable of weight.

Shape is fundamental, reflecting the distinctive outline of each insect group, like the tails of a mayfly, the extended body of a stonefly, the curve of a caddis or the bulk of a cicada. Size is critical and the easiest to judge when matched to an observable insect, but because fly size is inextricably linked to hook size having a choice of sizes in the fly box is an advantage. Ironically, when no fly in the box matches the necessary proportions, choosing one of contrary shape and size to what is commonly evident can be a successful tactic. Big fish, big feed, is a good adage.  If fishing two nymphs, use flies of different sizes and because it’s easier to hold fish on larger hooks, start large and change to smaller flies as need be.

Profile relates to style and with dry flies it’s the way they float on the surface; high-profile like a Royal Wulff or Stimulator, mid-profile like many caddis and CDC patterns or low-profile like parachutes, spinners and emergers.

For nymphs, profile relates to whether the fly is rough-dressed like a Hare & Copper or smooth-dressed like a Pheasant Tail and some caddis patterns. What profile is best may seem tricky to judge, but the simple benchmark is the character of the water being fished. Where the water is rough choose higher-profile dries or rough-dressed nymphs, and err towards lower profiles and smoother dressings in quieter waters.

Colour is only occasionally the principal influencing factor (as in match-the hatch situations) and is generally more important in nymphs than dry flies. Key colours include tans, browns, olives, greens, yellow, grey and black. Choice is frequently a process of elimination; for example changing light for dark, olive for grey, dull for bright. Many modern flies also make use of attractors like crystal flash, bright-beads or coloured foam. When the ‘right colour’ is elusive, some ‘instant fly colouration’ with indelible marker pens to darken the colour of light flies or change the colour of beads is a handy trick. Black and brown felt pens work best, and are always present in my fishing vest.

When trout don’t react to drifting nymphs, it’s often because the flies aren’t sinking deep enough. Nymph weight is a critical factor and knowing precisely how much weight is hidden in the dressing is an advantage … a good reason to learn how to tie your own flies. Often this weight is copper or lead wire, but bead-heads, especially tungsten, have been a revolutionary innovation, making heavy weight in small nymphs possible without increasing their bulk. Other ways to gain depth include adding split shot to the leader, or a heavy nymph as a ‘bomb’ with a small fly on a dropper behind. When trout won’t come up’, get the flies down. Judging when not to use much weight is also important, like when fishing shallow riffles or to trout feeding on subsurface emergers.

Initial fly selection should be based on what is visible. Don’t insult the trout feeding in the middle of the stream by expecting them to be feeding on the same insects found under the rocks in the edge-water, as they are totally different habitats. Learn to choose appropriately, because each type of environment in a river has different associations of insects.

When a fly is obviously not working, be flexible and change patterns regularly to suit the water. Repeat any successes (“success breeds success”), and make sure you keep a reasonable supply of previously proven flies in your box. There’s nothing worse than running out of a ‘killer pattern’ in the middle of a feeding frenzy. Eventually, through experience and increasing success, favourite patterns will emerge for different situations and the range in your fly box will expand. Ultimately, you will learn that there are very few ‘rights and wrongs’ when it comes to what fly pattern to use … fishing a fly with confidence is a huge part of the key to success.


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