Mayflies of the Snowy Mountains & Monaro Part 1

In the first of a two part series, Paul Bourne looks at
his local mayflies from an angler’s perspective.

Mayflies could be the single most important insects in flyfishing and they’re certainly the most revered. It’s even possible they’re the reason flyfishing began: Aelinius’s famous record from the 2nd century A.D. describes early flyfishing on a river in Macedonia. All those centuries ago, the trout being targeted were apparently jumping for small insects, quite likely mayflies. Right through flyfishing’s history, talk of ‘hatches’ has been dominated by mayflies, while more than half the known trout fly patterns have been tied with mayflies in mind.
I often wonder if these delicate and delightful insects were created for flyfishers through some sort of divine intervention – the two definitely seem made for each other! The unique lifecycle of mayflies (they’re the only aquatic insect with two winged stages) gives the trout plenty of opportunities to feed on them.
Most of a mayfly’s life is spent as a nymph, occasionally migrating or swimming about. Then, when the time is right, the nymph ascends to the surface to hatch into a mayfly dun, the sub-imago, which floats on the surface until its wings are dry enough for flight. The duns then spend time resting in the bankside vegetation (as little as minutes for some species through to a day or so for others) before a final moult into the adult mayfly spinner, the imago.
It’s the ‘hatching’, followed by the return of the adults to mate and lay eggs on the water before falling spent, which attracts the most interest from flyfishers. This cycle has been covered exhaustively in flyfishing literature since the days of Juliana Berners. Globally, flyfishers still debate the merits of various patterns and presentation techniques, but until someone manages to probe a wild brown’s brain with electrodes, we’ll never really know what the buggers are thinking!

The Snowy/ Monaro
A couple of decades ago, the Monaro district was probably considered the premier trout stream fishery in the country. That rating was at least partly based on the fabulous mayfly hatches that, under the right conditions, regularly occurred during spring and autumn. Various mayfly species would be encountered, but good luck to anyone who thought they could do well without some reasonable imitations; the label ‘technical fishing’ springs to mind! This wonderful, testing and rewarding trout fishery is hopefully on the mend. Meanwhile, the neighbouring Snowy Mountains trout fishery presently receives the most attention from flyfishers.
The majority of the rivers and streams in the Snowys are best described as freestone – rocky and clear, with a pebble bed and an occasional sandy/silty pool thrown in for good measure. There are also a few streams that, even though they are basically rain fed, resemble spring creeks. One of the wonderful things about the Snowy/ Monaro region is the variety of the waterways, each with a unique identity.
Understanding Mayfly
Mayflies are a good indicator of water quality and fortunately most of the Snowy Mountains and Monaro waterways are still relatively unpolluted and hold good populations of most types of aquatic insects. Mayfly are an important food source for trout and are high in protein. Apparently one kilogram of mayfly contains nearly double the protein of one kilogram of red meat. No wonder the trout love them!
Interestingly, many of the mayfly species that are found on the lower altitude Monaro rivers are also common in the mountains, while others only survive in well oxygenated flowing water.
So do we need to know anything about these insects? Opinions vary, but I’d certainly say yes! Latin names don’t catch more fish, but having a basic understanding of what the local trout are likely to be feeding on absolutely does, and mayflies are on the menu.
One thing fishing for the late John Sautelle’s ‘educated trout’ has taught me, is that these fish often won’t fall for just any old fly pattern. This is even more the case as fishing pressure has increased over the last decade or so. Other factors such as low water also have an effect on the catchability of these trout and it’s at the more challenging times that I find imitative flies invaluable.
I certainly don’t only fish mayfly patterns and my generic fly box is one I dip into regularly when I visit the mountains. Red Tags, Royal Wulffs, Elk Hair Caddis and the like are fantastic flies and you can certainly catch plenty of fish on them.

Predictability and Variation
You can never be sure when you’ll stumble onto a big hatch in the Snowy/Monaro region. The many different species of mayfly found in the mountains means good hatches can occur at pretty much any time of season, assuming conditions are right.
In the high country rivers and streams, we don’t seem to have the sort of hatches you can set your watch by and to some extent it’s usually dumb luck that sees us stumbling upon a good hatch with fish rising everywhere – an important reason to always be prepared.
The best hatches generally occur when there’s adequate humidity. Adult mayflies don’t have mouths and neither eat nor drink; they are delicate little creatures that will simply desiccate in dryer conditions. Stormy, humid days or cooler rainy days can both produce good hatches, while sometimes nice pleasant weather may be humid enough. I’ve even seen mayflies hatching in a snowstorm! Interestingly, when we were having non-stop rain through the last couple of drought-breaking seasons, I saw regular, smaller, ‘trickle’ hatches. It seems that if it’s been a bit dry for a period, then when there is a hatch, it will generally be heavier. I’ve also found that while there can be reasonable hatches during windy conditions, the duns tend to get off the water more quickly, which of course makes it tougher for the fish to catch them. This can result in less interest and response from the trout. There are certainly plenty of variables when mayfly fishing and luck is one of them!
The lower altitude streams tend to have insects hatching earlier in the season and high altitude waters see more activity over summer. Of course as the last few years have shown, the seasons do vary.

Local Mayfly in Detail
There are at least a few dozen species of mayfly in the Snowy Mountains and Monaro region, and probably just as many yet to be described. Only last season I saw a distinctive dun I’d never seen or heard of before. I’m definitely going to look a little more closely for it this season, but simply out of curiosity as it’s obviously not common enough to be important from a flyfishing point of view.
In this article and the next one, I’m going to list 10 mayflies I regularly come across during the season, five this time and five in the next issue (where I’ll also talk about collecting mayfly yourself.) For this project, I’ve simply collected nymphs of species I’m interested in, being the ones I find fish regularly feeding on. I then hatch them out and end up with pictures of the nymph, dun and adult spinner which accurately match the three stages. (There are numerous species similar enough to those covered here, and the same flies can easily work for them.)
Correctly identifying mayflies is a difficult business and after plenty of time studying the available literature, I’ve concluded it’s just too hard to be certain that some of the mayflies I’ll describe are a particular species. So in such cases I’ll list the family or genus instead. To accurately identify the more challenging examples would require access to all the available literature, a microscope, a very large amount of time and maybe a professional entomologist in your pocket – and I have none of these!
There are of course many other mayfly types besides those listed and you may find a certain piece of water that holds another species/type that’s worth consideration. For those who wish to do some research of their own there are some useful books as well as information online – both occasionally updated. I’ve listed some handy references hereabouts.
With each of the mayflies mentioned, I’ll suggest readily available patterns and sizes. No doubt keen fly tiers will use the images and information to devise their own patterns. I have my own ideas as far imitation and presentation goes. Like most people I believe presentation is paramount, and there’s actually a fair amount of imitation – how high the fly floats, how it moves etc. – built into the presentation itself.
Knowledge and observation are two of the flyfisher’s most important skills. If you’re a flyfisher visiting the Snowy/ Monaro region, hopefully the following information will prove useful. It will give you an idea of the mayflies you are likely to come across, and by extension some useful flies to try.

Nymph
Size 12* brown seals fur.
Dun
Size 12 Adams, or for more difficult conditions a Pecks or Highland Dun.
Spinner
Size 12 or 14 Black Spinner. (As with most mayflies, the late season flies can be smaller than the early season ones.) *All hook sizes listed relate to a standard dry fly hook, e.g. a Tiemco TMC100.

Atalophlebia albiterminata (genus & species)
This is the Big Black Spinner, also a Leptophlebiidea. This mayfly is very widespread – it’s the same one you’ll find hatching on Little Pine Lagoon in Tassie. It’s found in a fairly diverse range of habitats.
The big hatches on lowland (Monaro) rivers were more often than not Black Spinners. They’re common in the Eucumbene and other mountain rivers as well. No doubt there are a few very similar species in the region.
Depending on the year, you may find these mayfly hatching somewhere from opening day till the end of the season. Their oxygen requirements aren’t high but they don’t mind some flow either. They’re in the pools on the mountain rivers, but like most mayflies, they lay their eggs in riffles and runs. I don’t often see them too high up (above 1400 metres.) The nymphs are readily found under rocks in quieter water.
When the Big Black Spinners are mating and egg laying, the trout regularly leap right out of the water for them and these fish can be hard to catch – ouch!

Nymph
Size 14 Grey Darter of Norman Marsh fame.
Dun
Size 14 Iron Blue Dun.
Spinner
Size 14 Black Spinner.

Tasmanophlebia (genus)
Like many Australian mayflies, these have relatives overseas and this genera has species that in the nymphal form resemble New Zealand’s Grey Darter nymph. That’s the phase of most interest to me – which is unusual as I’m definitely a lover of the dry fly.
The nymphs tend to crawl out of the water to hatch and therefore the duns aren’t as available as those of other river mayflies. The spinners are primarily black and not too distinct from other black species so if they’re about a standard Black Spinner will do.
The nymphs are a bit unusual as they are a semi burrower that seems to love basking on sandbars and edges of sandy pools – just waiting for a hungry, cruising trout. When startled they dart 10 to 30 cm before settling again. That should give nymph fishers a bit of food for thought! The imitation makes a great ambush fly.
This mayfly seems to prefer rivers with some flow and therefore a bit of oxygen it seems.
I regularly see the nymphs in pools on mountain rivers from late spring to early autumn.

Nymph
Size 16 or 18 Pheasant tail nymphs – you can go smaller if you like!
Dun
Size 16 to 20 Blue-winged Olives with a few paler size 16s for the Cloeon.
Spinners
Size 18 orange, cream or brown.

Baetidae (family)
Offadens and Cloeon are the common Genera of Baetis of interest and for mine they’re similar enough to be covered together here. Size is the major difference with the larger Cloeon common in quieter, lower elevation waters and Offadens regularly found in most flowing streams and rivers at higher altitudes (above 1200m.) Some Baetidae species are tiny – they’re our smallest mayflies and can be as minute as a couple of mm long; size 28 or even smaller if you bothered to try imitating them!
The small nymphs don’t interest me as much as the duns. Trout seem to go for them over other offerings when they’re about. These are BWO’s or Blue-winged Olives and although I’m sure the Baetis found overseas are only distant relatives to ours, they certainly seem to have a similar appeal to the trout.
The larger Cloeon duns are a little creamier but standard patterns will suffice. The nymphs tend to be found browsing on weed in slower water and that’s where to look for them. The smaller fastwater species’ nymphs live under rocks and debris. They’re all quite agile swimmers.
The adult spinners vary in colour from tan,
to orange and some are cream. As in many mayfly species, the males tend to have larger eyes, longer forelegs and are usually a bit darker.
They hatch throughout the season and sometimes in good numbers in autumn at medium/lower altitudes. The higher altitude species can hatch in big numbers through late summer.

Both the hatches of the fawn-coloured dun and the afternoon spinner falls seem to interest enough fish for me to carry an imitation. Again, they are common from mid spring (or earlier on lowland streams) to mid autumn.
There are definitely a few similar looking species that are adequately covered by imitations of this mayfly.
I’ve regularly found duns hatching throughout the day. The nymphs tend to be found under rocks and stones in moderate to low flows.
The adults (spinners) are delicate so I’m sure to use a sparsely tied fly.

Nymph
Size 10 or 12 brown with a bead-head, so they’ll get down in the flow.
Dun
Size 10 or 12 Adams – the mottled grey/brown makes a fair imitation. Make sure they’re well hackled in spring flows.
Spinner
Size 10 or 12 Adams again, as in afternoon light the colour seems less important; sometimes clipped a little. I’ll sometimes use a big Macquarie Red instead, depending on the species.

Coloburiscoides (genus)
There are a few species of Coloburiscoides in the Snowys – these are the iconic ‘Kosciuszko’ mayflies. The most common is Munionga – the dun and spinner of which is shown here.
There’s a bit of colour variation depending on the watershed and the huge Giganteus dun is far fleshier in colour and some have a redder-coloured spinner.
The main thing with Kossie mayflies is they’re big, really big. I tend to use a size 10 or occasionally an 8 or 12. The biggest ones are less common and don’t tend to hatch in such great numbers. They also tend to be in the higher altitude streams.
Coloburiscoides are regularly found in most of the region’s flowing streams and rivers. The nymphs need plenty of oxygen (hence the large gills) and they are found under rocks in runs, riffles and heavy water. Fortunately, the trout seem to feed up into the run when they’re hatching, so the turbulence can make things easier for angler. However, there will always be a cautious brownie a little further back, sipping along the bank.
I find the Coloburiscoides duns hatching from mid spring till mid autumn and the timing and location of good hatches can be hard to pick. Still, they are common and there are often a few Kossie duns coming off at any time.