The Dun Thing

Philip plans for the mayfly season ahead.

It’s spring, and a not-so-young man’s thoughts here in the central highlands of Victoria turn to… mayfly. Both as a guide and an angler, I have a love/ hate relationship with these benign yet beguiling insects. From around late September, I try my best to head out on the lakes without feeling dependent on encountering mayfly. Or more specifically, mayfly duns – the sub-imago, or in other words, the newly-emerged mayfly. (Yes, the late lifecycle stage mayfly spinners can be a thing too, but I only have so many pages.) Being adaptable is part of being a successful flyfisher, so it doesn’t pay to have your fishing day hinge on the presence of an insect whose presence can be unpredictable, and certainly beyond our control.

Come dun season, I try not to make my lake fishing too mayfly-dependant, although with the possibility of big trout like this slurping off the top in the middle of the day, the lure is great!

The problem is, when mayfly do emerge, the fishing can be about as enthralling as it gets. Trout really do love mayfly: especially the nymphs and duns, and the emerger stage inbetween. Depending upon your interpretation of the notes of a Roman traveller nearly 2000 years ago, flyfishing may have been first invented purely to catch trout feeding on mayfly.

Mayfly in general are little understood: they don’t sting, destroy crops, pollinate, or spread disease – which shoves them way down the pecking order for scientific research. Say the word ‘mayfly’ to any of those poor people who don’t flyfish, and you’re likely to get a blank stare, or a request to repeat what you just said, because they must have misheard.

So, due to this lack of scientifically rigorous research, for most species, we can only guess at the details of their lifecycle, including what makes a good mayfly season (including duration), and what prompts a good dun hatch on any given day. For the main stillwater mayfly species in Victoria, Atalophlebia australis (aka Lambda Dun, Turkey Brown), I’ve done my best to keep diary records from year to year over several decades in an effort to fill in the large gaps in the science. But unfortunately, in many cases, it’s proved to be a case of the more I know, the less I know!

Lifecycle

Life begins for A. australis as a tiny fertilised egg drifting down in the water column. The egg hatches into a nymph, which then crawls around feeding on organic matter, while keeping out of sight of predators. The cover provided by woody debris, gravel /rubble, and particularly aquatic vegetation, seems important for nymph survival. If a good mayfly water temporarily loses its weed-beds – as can happen cyclically on many lakes – the hatches often suffer. The nymphs are weak swimmers, and once caught out in the open, are easy targets for predators like fish, diving birds and other insects.

After a poorly-understood period – probably a year; possibly in some cases two years – the nymph is mature. When conditions are right or it has run out of body clock hours (more about this later), the nymph swims to the surface and uses the surface film as a platform to wriggle out of its ‘wetsuit’ nymphal skin. The wing-case above the thorax splits, then the wings pop up vertically and quite quickly. (See my short video at the end of this article.) Once the wings dry, and the dun flutters weakly to the nearest bit of bankside shelter.

What all the fuss is about.

Crucially, the ascending nymph, the emerger (the nymph in the process of emerging as a winged dun) and the dun itself, are all candidates for the attention of the trout, although during any hatch on any water, the importance of these three forms can vary enormously – and their appeal can even vary from minute to minute, let alone hour to hour.

Having made it safely to the cover of a bush, reeds, long grass or some other upright surface, the dun soon sheds yet another skin – even over its wings (weird, but true!) – and takes the form of a brightly beautiful reddish/ orange spinner. Unlike it’s camo forbearer, the spinner is briefly a strong flier… until it’s reserves of energy and fluids are burned up by mating rituals and egg laying, and it lies on the water mortally depleted.

Once eggs are laid by the females, the cycle begins again. (Incidentally, on some fisheries, such as the rivers of Tasmania’s midlands, the A. australis spinner, not the dun, is the main game for flyfishers. But for us Victorians, the spinner stage tends to come second in importance, despite periodically producing good fishing.)

What makes a good mayfly year?

All other things being equal, wet years seem to favour dun hatches over dry years, and as there’s uncertainty over A. australis lifecycle (sometimes one year, sometimes two years… and there is an autumn cohort and spring cohort), it would make sense that a succession of wet years is the most favourable… and so it seems, up to a point! However, my diaries show good dun hatches and fishing at Hepburn Lagoon in mid-April 2011, less than a year after the breaking of the ‘noughties’ drought (winter 2010). Keep in mind Hepburn was virtually dry right through the summer and autumn of 2010, so how did the mayfly recolonise to the point of reasonable hatches and rising trout in less than a year? Like I say, the more you know, the less you know!

Rob during a dun hatch at Hepburn Lagoon on 15 April 2011. The lake was all but dry 12 months earlier.

Conversely, there’s been the odd second or third successive year of good water levels when hatches have been disappointing. Still, outliers aside, water and plenty of it seems to be a positive.

As for exactly when in spring dun hatches can be expected to begin, that’s impossible to nail down, with no obvious correlations between previous and current weather or water conditions. On the Ballarat lakes (Wendouree, Moorabool, Newlyn, Hepburn, Talbot, Cosgrave, Dean etc.) a late September hatch is the best you can hope for, and a hatch worthy of the name may not happen until as late as mid-October. For finishing dates, early December is about as long as ‘proper’ dun hatches go, while some years, it’s all over by mid-November.

Hatches can begin somewhat earlier on lower elevation waters such as Lake Fyans.

For lower elevation waters with dun hatch potential, such as Konongwootong and Fyans, you can sometimes bring those starting and finishing dates forward a couple of weeks.

A few other points to note. I regard a hatch as occurring when there are enough duns not to have to look for them – they’re just there in front of you. Individual duns can appear many weeks before or after the dates above, and don’t seem to be any indication – good or bad – of ‘proper’ hatches to come. And individual duns aren’t much use to the fishing!

Finally, it seems likely that the odd hatch might occur during low light in summer, as summer spinners can sometimes appear without any obvious dun hatch beforehand. And very occasionally, I find a dun hatch in daylight in summer; usually in cloudy, damp conditions.

What makes a good mayfly day?

Assuming the hatches have begun, in late September/ early October, you would be unlucky to miss a hatch if you got to your dun lake by 12 noon EST, and left by 3pm EST. As spring wears on though, the hatches have a tendency to start later and finish later. Towards the end of November last year, we sometimes had hatches going until 5 or even 6pm EDT. (Don’t forget to make the adjustment for Daylight Savings when it comes in – the fish and mayfly don’t know what it is!)

Cloudy days are best for hatches, and cloudy and humid days are even better. One theory is that the duns don’t like to emerge if it’s too warm and sunny, because, having lost the ability to eat or drink upon transforming into duns, they will dehydrate more quickly. What is undeniable is that cooler, more humid conditions prolong the time to take-off for duns, leading to proportionally more on the water per emerged insect – and so a more impressive number of duns stuck on the surface. Be careful what you wish for though: a blanket hatch can create a situation where the trout have so many real duns to choose from, they can afford to bypass many of the naturals, let alone your fly!

Duns not going anywhere on a misty Moorabool day.

Wind is an interesting one. Purely from a dun’s point-of-view, wind probably helps dry their wings faster, but it can also blow them long distances across the water, landing and then taking off again.

Now for all that, you can sometimes get good hatches on bright or warm days, breaking the rules. I can only guess that this relates to that body clock thing I mentioned earlier. Perhaps, having reached maturity, the nymphs can only wait so long before they ‘have to’ hatch. If the right conditions don’t come along in time, they’ve gotta go anyway.

Tactics

On any day, it’s worth moving around to find the best dun hatches: it’s almost unheard of for hatches to be distributed evenly across a whole lake. Even better, fish with a mate, and spread out while keeping in touch. Concentrations of swallows, gulls and to a lesser extent waterbirds – even crows foraging on a windward shore (thanks Craig!) – can all be clues to where good hatches are happening. However, there’s no substitute for moving around while looking for duns on the water, and better still, rises.

Sometimes, particular bays and shores will produce for days or even weeks at a time. By all means, check these places out, but don’t be completely reliant. The action may eventually move to somewhere else on the lake; and often for no apparent reason.

If you do find the duns, a great position can be into the wind, or where the wind is blowing along the shore. Ripple will help get takes, and trout will often move quite predictably into the wind, allowing for better intercepts. Try to develop your offside and into-the-wind cast so you can capitalise.

A perfect spot at Newlyn to ambush dun feeders as the naturals drift out heading left to right.

Then again, there will be times when the greatest accumulation of duns occurs in calm water; either on a sheltered shore or in the lee of a point. While this can produce very exciting fishing, the track of the trout can be quite random, they’re easier to spook, and the fish can be more critical of flies and presentation.

As for flies, how long have you got? A. australis dun/ emerger imitations must be some of the most diverse patterns representing a single insect in my box – and I’m more of a presentationist than a fly junkie. I’ve included a basic list below, but fly features to consider include:

  • Visibility of fly for the angler (very important).
  • Size (can be important).
  • Colour, or more to point, light or dark (can be very important).
  • Where the fly sits – in or on the surface film; in other words, its ‘footprint’ (often very important).

And should you even use a dry? Sometimes, nymphs can out-fish dries, even when you’re seeing rises. A skinny brown or claret nymph with a dark wing-case, retrieved singly at a slow, steady pace or in a team with another fly (even another nymph) is well worth trying. Another idea to consider is suspending a nymph a foot or two beneath a dry.

Incidentally, when using a dry, my default is to fish it dead drift (i.e., static except for natural current or wind drift). However, sometimes a bit of movement can get attention, particularly with buoyant emergers like a Possum Emerger.

Whatever flies or tactics you choose, give them a good go. Presentation remains the key in all dun hatches, and sometimes – especially when there are lots of naturals – you just have to present with perfect accuracy and timing to get an eat. Time spent changing flies is time not fishing, something that’s especially a factor with a rise which may only last an hour or two.

Some generalisations

Trout often take dry flies/ emergers more readily early in the hatch, and sometimes more readily again towards the end, when dun numbers have reduced. The middle/ densest part of the hatch can actually be a more demanding time to fool a fish, and may even require a change of tactics, such as fishing a nymph on its own or underneath your dry.

This fish took a Brown Paradun early in the hatch.

Speaking of nymphs, there’s an argument for fishing a pair of nymphs subsurface (simply cast and retrieved with a slow/ steady hand twist, or under an indicator) while you wait for the hatch to start, and again after the hatch is over. Fishing nymphs alone can also save the day when there’s a good hatch of duns, but few if any trout rising. I’ve had this happen quite often, and once I’ve gotten over the disappointment of not being able to fish a dry, nymphing has produced plenty of really good trout. It can help to get the nymphs down a bit too, maybe a metre or more at times.

Why trout will sometimes take nymphs instead of all those delicious duns on the surface, is one of life’s great mysteries. I guess we have to assume that, on such occasions, the nymphs must be easier, and perhaps ‘safer’, to catch. The trout can’t be refusing to rise just to annoy us… can they?

In a similar vein, if the hatch is sparse and rises few, Christopher Bassano taught me you can sometimes ‘fish up’ the trout retrieving a team of Possum Emergers. My brother Mark likes to do somethiung similar with a Claret Carrot dry, and a nymph about 60cm behind. Both tactics work best with ripple and an overcast sky.

One point about nymphing: on occasions, particularly at Moorabool and Newlyn, retrieved nymphs can be absolutely swarmed by small redfin before the trout get a chance to respond. If that happens, I stick with a dry and take my chances.

Autumn

I’ve mentioned autumn hatches. These usually occur between early March and the end of April. While not as reliable as the spring dun hatches, they can still provide great fishing, albeit for somewhat shorter periods. Autumn dun tactics are similar to those covered above, although it’s worth noting that the duns are often smaller and lighter in colour.

In any case, autumn can wait because spring is the focus right now. Fingers crossed for plenty of good hatches.

FLYSTREAM FACTS – Dun hatch flies & gear

I like 9’6” 6 weight rod and a floating line, coupled with a good reel with a decent drag and lots of backing – there can be some big dun feeders on the Victorian lakes. And of course, always carry a big, easy-to-deploy landing net.

All the gear at Newlyn, November 2022.

For flies, the list could almost be endless, but must-haves include:

  • Possum Emerger in light or dark shades (size 12-14)
  • Brown or claret Paradun (size 12-14)
  • Brown or claret Shaving Brush (size 12-14)
  • Floating brown nymph (size 12-14)
  • Skinny brown or claret nymph (size 12-14)

If you fish the dun hatches in Tasmania, your fly collection should transfer well, with the exception that you may sometimes need flies a size or two smaller on the Victoria lakes.

Finally, to quote Molly, do yourself a favour and use high quality tippet in 3X as standard, maybe 4X if you need something finer for small flies. Total leader length of about 11-12 ft works well for me when fishing a single fly or a dry with nymph dropper.