Mayflies - the fly and the fishing

by Daniel Hackett

There's something about mayflies, something significant. To the flyfisher they are the epitome of flyfishing - predictably unpredictable mesmerising creatures reeking of mother nature. I think it could be the mayflies ephemeral nature that is so mesmerising, fleeting slivers of beauty, existing above the water's surface for only a matter of hours. They are an order of animal that was given the title Ephemeroptera, derived from the Latin for short lived. Looking at a small dun one day I realised that I was staring at a small living glimpse of prehistoric artwork and furthermore that I was the only person in the world who would ever see it. Perhaps this why they're so special?

Mayflies for beginners
The mayfly begins its life like most things, as an egg. Mayfly eggs live underwater in places of shelter - woody crevices, under rocks or amongst dense weed. Hatching out of the egg is the nymph. Nymph is a term used to describe a stage in the life cycle where an organism is immature, rather than a term describing a specific animal, in this case the mayfly. For the young beginner the nymph is best described as the "caterpillar" life-stage of mayflies. Mayfly nymphs in Tasmania are typically small, of the common species their size ranges from 1 to 2 cm or size 10 to 16 in hooks. They are usually brown in color and have a body consisting basically of a head, abdomen (legs out to the sides) and a tail. If your in to fly-tying then nymphs made out of pheasant tail fibers or chocolate brown seals fur are about the right color 90% of the time. Nymphs move around by crawling or swimming, with swimming being achieved through a mermaid like movement of the tail. The nymph is the life stage of the mayfly that fish eat most with predation occurring as the nymph sits on the bottom, crawls around, swims or when it is hatching.

As mentioned the "nymph" is a depiction of a life stage and the next stage in the mayflies life is when the mayfly becomes a dun or sub-imago. For reasons of simplicity I'll refer to them as duns. A nymph develops into a dun by hatching, which typically involves a nymph swimming to the waters surface or climbing out of the water and shedding its outer layer of skin. From inside this layer of skin an insect crawls out with the body of a nymph but now with wings. When this hatching is occurring the nymph / dun is referred to in fishing terms as an emerger. Quite often on a river or lake a dun will seemingly pop up from nowhere to be sitting on the waters surface like a little wind-surfer, this occurrence being due to the dun emerging from its old body to be resting on the water's surface. The dun has to dry its wings out before it can fly and this occurs as it drifts along the waters surface or rests on a reed or rock. A mayfly will typically remain in the dun life stage for a time ranging from hours to a few days during which they may rest in bankside vegetation. Duns do not eat and in fact do not possess a functional mouth as their only purpose now is to breed.

At the emerger and dun stage fish often feed on mayflies. Typical rises (fish eating the fly) appear as small bulges or rings at the water's surface when the fish are feeding on emerger's, whilst rises where the fishes head and / or part of its body come out of the water are more so typical of fish feeding on duns. For the fly-tier good patterns include the Lodge Emerger, Shaving Brush or Possum Emerger when the fish are taking emerging duns, or try Highland duns or Parachute duns when the fish are taking duns. Remember emerger flies need to sit in the surface whilst duns sit on the surface.

When the mayfly is ready to mate it again undergoes a metamorphosis where the dun sheds a layer of skin (typically whilst in the rushes or on the bank) and is now at a life stage where the insect is referred to as a spinner or imago. Mayfly spinners are typically brighter than the dun. In Tasmania most spinners are dark black, with a few exceptions such as the famous red spinner and the not so well known baetid referred to as the blue winged olive (olive body). At this point in life the mayfly probably has only a few hours to live, so their main goal is to copulate and reproduce. Males will often form large swarms or "clouds" above the water surface where they wait to impress any female that might fly past. At this point the fish may leap out into the air to grab the spinner. When the male impresses a female they will mate and her eggs will be fertilised. Following this the female will generally move to the water surface and deposit her eggs.

The mayfly enters its final but briefest life stage at this point where the spinner is said to be spent. Normally present at dusk the spent spinner is the dying form of the mayfly and is best described as just that, the dead insect lying on the water. Again at this stage they are prime trout tucker and are imitated with sparse hackled flies with spread out wings. The flies sit in the surface.

The intelligent angler - catching mayfly feeders
In Tasmania we have some legendary fishermen. Some are locals, some are legends but I believe they all have two things in common that lead to their success. To quote Dick Wigram from his book "The Fly" he tells us about a young man Noel Jetson - "(He is) a very skillful angler who can think out the problems we all meet at the waterside". Skill and thinking are what I believe to be the two common ingredients to success on the water. Skill is attributable to natural talent, practice and a negligible proportion to equipment whilst thinking is something you do or have to teach yourself to do.

I believe that "thinking" on the water involves being observant and asking questions - "why did I catch those fish around the rushes" or "why did he take the claret coloured fly over the black one"? I'm not claiming to be the "Grand Yoda" of trout, a belief in the need for thinking anglers is nothing new. Early last century one of the forefathers of modern flyfishing, probably Frank Sawyer (an English river keeper and "inventor" of the Pheasant Tail Nymph) stated something along the lines of "if only anglers would pay more attention to the food of the trout and how they act they would be far more successful". Where is this going? If we think about mayflies we can learn a lot about where to find them and more importantly find fish. For this I will use a few examples:-

Q1. My work is situated along Brumby's creek and at times whilst driving the tractor I get dozens of duns and spinners landing on the bonnet or hovering just above. How could this observation help?

A1. The engine under the bonnet along with the exhaust of the tractor gives off heat, therefore the mayflies may be attracted to warm air currents. As a consequence I will look for sheltered pockets or bays on the water, out of the wind where there may be coinciding pockets of warmer air. Consequentially I may find larger numbers of mayflies an more feeding trout. Other sources of warm air currents could be breezes blowing of warmer land masses such as rocky islands or the land around small bays.

Q2. I recently watched a small nymph hatch to a Lambda dun and strangely I found it to hatch out with the red colour of the spinner only to dull to its typical brown a few moments later. How could this observation help?

A2. Lots of insects such as the damselfly often hatch out a different colour than they appear later on in their adult form. This could possibly be because the new skin has not yet dried out and firmed in the heat leaving it temporarily translucent? The significance of this could be that an emerger with a bit of claret or red in its body may be more effective when fishing for fish feeding on emerging Lambda duns.

Q3. Some mayfly species prefer to emerge into duns whilst hanging in the water surface whilst others hatch out on dry surface such as reeds or rocks. How can this knowledge help?

A3. The red spinner is typically an "in the surface" emerger whilst the small black spinner is a "crawling out" type emerger (FlyLife 12, Winter 1998). This knowledge is useful in that if you find red spinner duns (Lambda duns) are on the menu than a broadwater (with a suitable underwater habitat) may be as good a place as any to find feeding fish and emerging duns. On the other hand, if small black spinner duns are sailing past then fishing around structures such as tussocky shores, small tussocky islands or rocky outcrops may be a better place to find hatching duns and feeding fish.

Mayflies are a good example of what's out there to be learnt in the wide world of fishing. Get your kids involved and set up a bug tank if you can. If we can give the next generation an appreciation of nature and the aquatic world and by doing so instill in them a sense of responsibility then through a pastime we enjoy we might be able to start 'saving the World'. Maybe not the whole world, one of the important bits anyway.

Mayfly resources: FlyLife Magazine10-12, The Waterbug Book by John Gooderham & Edward Tsyrlin

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