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Corbie moths at dusk - testing time for fly fishing

by Tony Ritchie

Corbie moth time is at hand, and anglers on lowland rivers throughout much of Tasmania can expect to see some of the buzzing about over and on the water during the last light of late summer days suitably fine, calm and warm.

Any angling action to these corbies is usually brief, but can be hectic as big trout become very keen indeed on these meaty mouthfuls dipping down onto the water and gyrating about so temptingly upon it.

Our Tasmanian corbies differ from the bogong moths which in summer make epic migrations to the Koskiusko high country from pastures in Queensland and the NSW tablelands. In doing this, bogongs, understandably are at the mercy of strong winds - and considering that some have been blown away as far as new Zealand it's interesting, but hardly surprising, that a few of them have also been reported at places in our north east such as Mt. Barrow. 

The corbie, however, is found only in Tasmania. Emerging via a shiny brown pupa from the soil - and from the large, dark grey grub well-known to gardeners and to many of us when we were children, the grey-brown adult has a wingspan of about 4 sm and a bulky, bull-headed, fuzzy body about 3 cm long.

To complicate matters, the sseparate "˜winter"corbie which is found on the mainland and in Tasmania only in the north - and there mainly along the north west coast - has wings more of a red-brown colour. This moth hatches out between late November and late December, and in fishing central northern rivers I have seen it about in force only once - on the lower South Esk, on November 28 two years ago. However, anglers along the coast and in the north east may strike the winter corbie more often, and apart from the dates, the details which follow apply to it as well as to the more widespread native corbie.

This corbie "proper" occurs throughout the north, along the east coast, down the midlands to the Channel district and up the Derwent Valley. Although no doubt it blunders onto the darkening surface of many streams in these areas, fromt eh angler's point of view the larger rivers and broadwaters which give the trout in them a longer, better chance to "lock onto" it seem best, and personally I've found the lower Macquarie River between Longford and Cressy a suitable river to visit near Launceston.

The records I've kept on corbies since 1976 show that, while they may miss a year now and then, overall their hatches are fairly consistent. A few moths will probably be noticed towards the end of the second week in February but the main hatch usually begins in mid-month and continues for one and sometimes two weeks into March. Over the years, they have been particularly thick during the fortnight spanning February and March and, if asked to nominate the single best week, I would go for the last one in February.

Presuming that you have picked the right date, what else is needed?

Weather is critical, and ideal is a calm, warm evening, muggy but dry. Usually a chill will kill the hatch and, although a light breeze will be tolerated by many of the moths, it seems to turn trout into "oncers". If all is well with the weather, precisely where on the river would it be best to take up station at sunset?

Not required is a backdrop of shrubbery like blackberries and hawthorns, which reach sneakily out in the failing light to snare many a back cast. Clear banks make no difference to the corbie moths, which indeed favour mating on the ground or grass stems and then like to lay their eggs among the cover provided b y coarse grasses. Clear banks also allow anglers to rush unhindered from one slashing trout to another because, although as with other trout insects, the ideal is a strong current to funnel together the corbies and to usher them in line past the rod. In practice normally, there are not enough moths on the water at any one time and it becomes very much a matter of "catch as catch can", so to speak.

Seeing just where that fish chopped - and then just how far away was the cast to it - is aided considerably if the stretch of water chosen allows you to face into the sun's afterglow. Take a look up into the evening sky to check how much lovely cloud cover there is, and if much of a moon is showing - and if there's plenty, try not to have it directly behind your casting arm.

All this may sound rather finicky, but if the essentials of time and weather are in order a low buzzing will signal that the precious moths are in flight, action will soon begin and with luck any lingering irritation is about to be well and truly swamped. 

On the line should be a lure which will float well - I have always used the dry fly, but it would be interesting to try small floating plugs or similar, presented discreetly enough upstream using spinning tackle. Flies to use on well greased leaders attached to floating fly lines could certainly include buoyant deerhair floaters such as the American Humpy, hook sizes 10 and 12 are called for and suitable Tassie deerhair ties are the Snowburner and the Corbi, which has a cigar-shaped clipped deerhair body tied on a 10 hook, hackle of brown partridge, bronze peacock he4rl head and wings of grey turkey-wing quill strips. Personally, I favour a 12 Black Zulu, an ancient English fly which floats well if the hackles are stiff enough and can also be used to imitate a large caddis.

When a fish slashes, the aim is to cover it as quickly as possible. The usual degree of fly fishing finesse is no longer required because nightfall is nigh, and with luck the big trout are getting into a feeding frenzy. Line splash is tolerated, and so is drag. Indeed, just for once deliberate drag helps - the idea is to cast out square with the shoreline or even slightly downstream, and to twitch the fly across the nose of that monster before it moves off. Sometimes if currents are slow, you may even need to strip in some line to make sure that the fly does drag. You can also afford to go heavy with tippet strength - time is short, and the last chore you need is to try to tie on a new fly.

If everything comes together at Corbie moth time, your hands will be shaking too much anyway!