FOSAF NEWS - Fly of the month: Quick Sink Corixa by Tim Rolston

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Overview:
I am very much of the opinion that in stillwaters, and particularly many South African stillwaters, the fish don’t become overly selective for the most part. The massive midge hatches and caddis emergences characteristic of waters in other parts don’t seem for the most part to be as common on our waters. Much of the time stillwater trout, unlike their moving water stream-based counterparts, basically have to move and seek out food, and that often means that they don’t know what their next meal is going to look like. They will feed opportunistically as prey becomes available. 
There are going to be times when there is something obvious happening, a midge hatch or an ant fall and in those circumstances most anglers are going to work things out pretty quickly if they are paying attention.

But the more common issue is what fly to fish when there aren’t any obvious clues, and for me that suggests an approach that if not “right” is at least not “wrong”. The described Corixa pattern was developed over time when I was still doing a great deal of bank-based fishing in stillwaters, some of which sported massive concentrations of these aquatic bugs. 
Corixa have been known about for a long time and yet they are neglected in most angler’s fly boxes, to be frank I don’t really understand why. They have number of advantages above being relatively easy to imitate:

Availability:
Firstly: most trout waters are going to contain some Corixa and may well have thousands of them plying their trade in the shallows.

Secondly: they are there all the time, much like dragonfly and damselfly nymphs, at least you know that there are likely to be some about. So something of a reasonable bet if one has little other information to work on.

Thirdly: Corixa don’t have pupal, nymphal, larval, imago or sub-imago stages, you just get smaller ones and large ones, so it is remarkably simple to come up with a suitable pattern, far more so than with other potential food forms with so many different stages.

Fourthly: Whereas most other bugs “hatch” out by rising to the surface and making themselves vulnerable to trout predation only once in a lifetime, corixa, due to their need to retrieve more oxygen from the surface make this perilous journey numerous times a day. Sure they are not hatching but they are making themselves vulnerable in the same way and over and over again. Be assured that the trout know about this.

Fishability:

Because of the need for the naturals to be able to gain the surface to obtain air, and then swim against the buoyant effects of their own personal aqualung they tend to inhabit relatively shallow water. Which puts the areas to fish the artificial well within the reach of even moderate casting skills.

I don’t believe that these patterns are as effective fished from a boat, particularly one which is drifting. The naturals move relatively slowly and absolute control of the retrieve is important. For the most part I would suggest a very slow and erratic retrieve on a floating line. Watch for takes on the line or leader don’t expect to be feeling a “tug” to indicate a take, trout intercepting relatively slow moving patterns don’t need violent acceleration and takes can be very subtle. Strike at every hesitation of the line, sometimes it will be weed and often it will be a fish.  

It is likely that as many other food forms do build up gases around them when hatching, even if the fish are targeting something else the little spark of light from the silver body may well be enough to illicit a response even for trout not focused on corixa at the time.

Other fishing considerations:

It has been my experience that due to the shallow habitat of most corixa the fish can be reluctant to target them when there is bright sunshine and flat water. The best times to seek out fish feeding on these bugs is early and late in the day when the low light levels allow the trout to feel more secure in shallow water, or on days when there is a good ripple. Fishing into the wind on a shallow bank can be highly productive even when the sun is shining.

Fly Design:

In essence things could rarely be more simple, but simple and effective flies are not always as easy to get right as one might think. This pattern has been modified over time and the use of UV resins has made it probably an even better pattern now that it was in the past. 
The key features are the shape (a flattened oval), the prominent swimming legs and the silver bubble of to imitate the air trapped around the body. I also think it a definite advantage to tie this fly on a down eyed hook, on slow retrieves it will flip over and back again, sending out a little flash which can be easily seen when fishing clear water. This acts as an attractive trigger which can pull in fish from some distance.  Don’t be fooled by commercial patterns fancifully suggesting a trail of bubbles behind the fly imitated with crystal flash or similar, we are trying to imitate a bug surrounded by a pocket of air, not a miniature torpedo.

Materials:

As mentioned it is often harder to make things simpler, the fly uses only two materials other than the wire or lead underbody and the thread. Pearl or silver crystal flash or similar and Pheasant Tail Fibres. (the modern versions are coated with UV resin as well). To avoid clutter the some of the Pheasant Tail fibres which form the back are used to imitate the prominent swimming legs.

Step by Step:

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1: Place a down eye nymph hook in the vice, sizes from 12 through 18 are pretty much standard with 14 and 16 being probably the most useful. Wrap thread in touching turns to the bend of the hook, (thread colour isn’t crucial, thinner thread is to be preferred). I use 18/0 for most of my flies.

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2: Wrap an underbody of lead wire, (for more lightly weighted versions you can use copper wire to the same effect).

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3: Tie in with open wraps of thread and then crimp the body flat with flat nosed pliers, (use smooth ones, not pliers with teeth on them). Flattening the wire helps give the correct profile to the fly. Don’t overdo the pressure or you will cut the wire and it will fall off. (make sure you leave some space for the whip finish later in the process).

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4: Add a drop of superglue and some more wraps of thread to secure the wire further and then tie in about six to eight strands of Pheasant Tail fibres at the bend followed by four to six strands of pearl or silver crystal flash. (Due to the severe step up onto the wire crystal flash winds far more easily and gives a neater finish than trying to use flat mylar)

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5: Add a further drop of superglue to the wire, this helps step the crystal flash up onto the body, and wind the crystal flash up the body to form a neat flat oval shape. Tie off just back from the eye of the hook leaving enough space for the head and whip finish.

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6: Pull the Pheasant Tail Fibers forward over the body to form a shell back. Keep the fibres on the top of the body, do NOT cut off the ends yet.

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7: Take two strands of Pheasant Tail fibres on either side and bend back to form legs. (These sometimes break so leaving the other strands in place gives you more options in case of error, only cut off the excess fibres when the legs have been formed).

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8: Once the legs have been formed clip off remaining pheasant tail fibres and form neat whip finish head. If you are using a light coloured thread you may like to colour it with black marker prior to forming the head to give a neater finish.

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9: The legs or the natural Corixa are quite pronounced, so I usually glue the two strands of pheasant tail together with varnish to give a thicker appearance. Once glued together you can trim them to length.

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10. In the original version I would then coat the fly with Sally Hansen Hard as Nails, these days the effect is easily gained with UV resin. Be careful not to lose the flattened profile of the natural when adding resin.

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11: The finished fly should have a neat flattened oval shape, obvious legs and a distinct bright silver/pearl ventral surface to best imitate the natural.

Finally:
Corixa and Backswimmers are technically different, however they can both be imitated successfully with the same pattern. Fishing these flies carefully and slowly over weeded shallows as dawn breaks or the evening shadows lengthen can provide some of the most memorable fishing you will ever enjoy. You shouldn’t neglect these bugs, the trout don’t.

Tim Rolston is a past South African Fly Fishing Team member, Certified Master Casting Instructor and author of two books on fly tying. “Essential Fly Tying Techniques” and “Guide Flies” available on line from http://www.inkwaziflyfishing.co.za/Inkwazi%20Bookshop.html

 

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