Dun Hatches on the Goulburn 

The observations noted here have been drawn from the cumulative experiences of the three guides at Goulburn Valley Fly Fishing Centre. We fish/guide on this river every day of the season and there is always some new piece of the puzzle being uncovered. We hope that this short introduction to our dun hatches helps you to achieve better results when visiting the Goulburn and helps you to unravel a little bit more of the puzzle.

Introduction

Most hatches of mayfly on Australian rivers are not well documented. This is not due to any real anomaly in regards to our trout rivers but rather the fact that we do not have many people who actually fish full time on their local waters. While we hear of huge emergences on waters such as the Madison in Montana and on many of the British Chalk streams relatively little is written about local hatches. While our hatches are not generally speaking as intense as some of those that occur in these more famous locales (their seasons are shorter and more intense) there is some fantastic fishing available on the Goulburn River for those targeting the emerging Mayfly.

When?

Goulburn River hatches of Mayfly can occur at anytime of the year. Unlike many other trout fishing destinations, a relatively mild climate means that it’s never too cold for Mayfly to appear. We often have Mayfly on both the first and last days of the season in September and June and on most days in between. Even in July last year while filming spawning fish we encountered good hatches and rising fish.

Blue Winged Olives

These tiny duns are associated the world over with cold weather and the seasons end. On the Goulburn we get weak hatches of them in spring and they are usually the first of the Mayfly family to appear. However it is the low water conditions in autumn that most of us look forward to when thinking about BWO’s. Their arrival is usually heralded by the first real frosts after the river has dropped. Cold, clear and low flows are required for the best hatches and the best month would have to be May. Characterised by flows of 130 Megalitres per day due to the cessation of irrigation demand this last month of fishing before the season closes is pure magic.

More often than not May consists of windless days and heavy fogs that don’t lift until lunch time. The first of the duns appear about 10 am and it is possible to find fish already dining on them however catching them is not easy with every movement being silhouetted by the thick fog. Not long after 11 am more duns appear and the fish all seem to have taken up residence in the slow flowing bubble lines for an easy feed. At times there appears to be hundreds of fish rising with heads breaking the surface as far as the eye can see to take advantage of the feast.

Presentation is of the essence. A four weight is considered overkill with most settling on 2-3 weights in the still conditions. Leaders average about 12 feet in length with at least 3 feet of two pound tippet. The fly is all-important. You will remember back in summer when a beetle was a beetle was a beetle. Well things have changed and you better get organised if you are to share in the spoils. Small to tiny flies are needed. Starting at #16 for the faster water down to 18-22 for most of those found in the bubble lines. Parachutes, No Hackles and Comparaduns are used with as close to the exact shade of olive for the body and slate grey for the wing as possible. Ignore this advice at your peril.

This fishing stretches most years until seasons end depending on when the real rains come which are usually in the first three weeks in June. Fish supposedly with their minds on spawning will rise quietly all day. The best fish I have seen taken on a Blue Winged Olive pattern went close to five pound and the biggest bag days went well over 50. I would quote the actual number but I have been accused once this season of exaggerating so will leave it at that. In recent seasons the olive hatches have not been as good as in previous years and this can be directly attributed to a low lake level. This year we have a fair amount of water left in the lake and if it stays this clear and cold for the rest of the season we should see some fine fishing for the month of May.  

Kosciusko Dun

Colloquially named the Kossie Dun takes its name from Australia’s tallest mountain. Quite fitting it being one of our biggest duns. Kossie Duns are found along the Great Divide in South East Australia and every year they are documented in systems they were previously not identified in. From up in the Snowy Mountain's Geehi to the Goulburn River at our back door, the phrase the Kossies are on conjures up vivid images in the minds of all flyfishers who have crossed paths with these outsized ephemerids.

Kossie Duns can hatch in large numbers anytime from late October until April although November and March seem to be peak times. They inhabit the fastest stretches of a river and therefore fishers favour much of the Breakaway and the area downstream of Gilmore’s Bridge. These are fast stretches of water with gravel bottoms, and therefore are supremely suitable for kossies.

Summertime emergences often occur in that last light so favoured by flyfishers. Hatches are often huge in volume of insects and last only 10-20 minutes sometimes extending well into darkness. Autumn and spring can be somewhat different with ideal temperatures triggering hatches in the afternoons and this can lead to some of the best fishing of the season. Large fish are often drawn to the surface to feed and when this happens in broad daylight there is not much more you can ask for. Even better is the fact that imitation is almost restricted to the dun only. Forget tying emergers in just the right colour. These mayfly are fast water lovers and are therefore accomplished swimmers. They leave the stones at the bottom and swim strongly to the surface where they break through the meniscus very quickly. This means that the fish don’t have the luxury of targeting a small, helpless insect trapped below the surface tension and must grab the nymph on its way up or take the dun in the second or two it is on the water. This leads to very aggressive surface feeding and in the low light the fly only need be suggestive. Daytime emergences are similarly frantic although we would recommend a parachute or thorax tie at these times.

Five weight rods are the norm for fishing this hatch on the Goulburn and 5-6lb tippet can safely be used to tire fish quickly and give you a chance for another fish before it gets dark. Hooks should be barbless as the flies needed to imitate this insect tend to be large. Patterns should be cream-grey coloured in the body with a grey wing sufficing. Don’t use traditional hackled flies as these have a tendency to fall over and not present right. For an example see our Kossie Dun pattern that is tied by using a normal hackle that is then clipped underneath before being used.

Rusty Dun

This is the mainstay of our Mayfly fishing. For many years now we have been imitating this beautiful little fly that thankfully the fish appreciate as much as we do. A dark Rusty Brown colour with a dark wing it appears anytime from mid-October until May. It is mainly a #16 although occasional specimens may be a size bigger or smaller. It is a late afternoon and evening emerger in the warmer months but can appear after midday during the more mild conditions of autumn and spring.

This insect can be found in most sections of the Goulburn upstream of the confluence of the Acheron River. The larger summer hatches can be directly attributed to a falling river and often a cold southerly wind, which often sees massive numbers of this mayfly hatch. Dun hatches comparable to other parts of the world occur with up to a 20 duns per square metre of water surface not being uncommon. These hatches bring the fish to the top like never before and some outsized fish are caught this way every year.

As this insect hatches so regularly throughout the season and sometimes the day, and because it is rather small (can't break through the meniscus easily) all stages of the emergence need to be imitated. Fish on these mayfly can be very picky and getting the fly and presentation correct are crucial to success. First off you have to be confident in picking whether the fish is taking the adult or the emerger. Many American fly fishing writers speak of the ‘pounds of meat’ theory. Basically that is that fish will feed on whatever stage of whatever insect is most prolific at that particular moment switching between them as the hatch changes. Quite often to the angler, what they think is happening and what actually is happening are two different things. Often large numbers of duns on the surface sees us fishing to the wrong part of the hatch. It is very possible that there are still more emergers stuck below the film than there are duns on top of it and the fish will soon tell you this with persistent refusals. The most basic of pointers when fishing these hatches is to watch the riseform. Is the trout actually breaking the surface with his snout or his back? If a fish wants to take a dun he must lift his snout out of the water and take it from the top. This is very easy to spot when you look in the right place. Often a noise will be omitted and always a few bubbles will be left as an indication that the fish is taking from the top. This means he is taking duns and a parachute tie will suffice. However if the breaking of the surface is by the trouts back it is a fair bet that he is on the emergers. Often the surface will not be broken at all and what we call a ‘push rise’ will be the only sign of a fish. This occurs when a fish takes something just below the surface and it is noticeable by small waves in the flow that many mistake for the current. When this occurs you can safely guess that emergers are being taken and a brown Klinkhammer or floating nymph will often work.

A method sometimes favoured by those not confident in picking the riseform is to fish both the dun and an emerger a little ways behind it. This can cover both stages of the hatch and give you an each way bet. The Rusty Tailrace Dun is far and away the best fly for matching this particular hatch and has needed little modification since its original design some seven years ago at time of writing. Carrying a selection of Pheasant Tail Nymphs, Brown Klinkhammer’s and Rusty Tailrace Duns in Sizes 14-18 should see most situations covered when this insect emerges. No specific tackle is needed but you must get the fly to drift right over the fish. Most hatches of this mayfly are quite large and often the fish will not deviate from the driftline to intercept the fly and so accuracy is very important. Four to five pound tippets are considered normal and the need to go thinner (down to 2lb) may only arise in the flattest of water.

Patterns

Too many people fish traditionally hackled flies out of habit rather than looking deeper. By traditionally hackled (call it ‘old style’ ) we mean the hackle wound around the hook shank so that it sticks out at right angles from the hook. This is not a good representation of a mayfly dun. Duns don’t sit up high with their body out of the water. Much of their thorax and abdomen actually sits in the film and these ‘old style’ flies do not accurately represent the natural. A parachute hackled fly, with the hackle wound horizontally around wing post is a much better option. Firstly it lands correctly every time unlike the ‘old style’ which would be lucky to sit correctly 50% of the time. Then you have the profile of a dun, which the parachute tie imitates much better. Leaving the body low in the film like the natural and having a clearly defined wing, parachute ties have revolutionised the matching of this hatch world wide. Wings should be at least equal in length to the hook shank as anyone who has viewed a dun from underneath can verify they are about 75% wing!!

The only alternatives we see is in the use of Comparaduns, Thorax Duns and No Hackle Duns. These are all similar to parachute flies in that they try and give that low riding profile similar to the parachute dun (or paradun as we like to call it). Of most interest is the Thorax and No Hackle Duns. Thorax Duns are tied with an ‘old style’ hackle and then trimmed with scissors to sit correctly and lower to the water. These are especially handy when tying duns to be fished in faster water where the fish don’t get quite such a good look and where the difficulty of keeping the fly afloat is great. No Hackle Duns are ideal for fishing to those fish rising to duns in the slowest, flattest of water usually associated with spring and autumn. As such we only use them when fishing to BWO feeders in May. They are fiddly to tie and not durable at all and we will therefore fish a parachute tie and if a particularly fussy fish is encountered we will then switch to the No Hackle.

Last Word

For too many years most of us believed we had to go overseas or at least interstate to encounter good Mayfly hatches. Many of the countries most published fishing writers have certainly given this belief credence. However, the Goulburn River has some of the best Mayfly hatches to be found in Australia and hopefully armed with a little bit of knowledge you can share in what up until now has been the domain of the guides and a few local anglers.