Hook Size: 14/16
The Perfect Fly Light Cahill Dun is an excellent imitation of the adult stage of life of the mayfly. It imitates the mayfly as it drifts or floats on the surface, drying it wet wings enough to fly off the water onto the banks, bushes or trees where it will eventually change into the spinner stage of life. It even imitates the dun down to two or three tails and it two upright wings. It is fished on the surface as a dry fly. It should be treated with floatant.
The Light Cahill duns don’t spend much time on the surface of the water. They
hatch well into the season and the water is usually in the mid fifties to sixty
degrees. The warmer the weather and water, the less time they spend on the
surface. Their wings dry fast and they usually depart the water within seconds
from the time they hatch.
Theses mayflies hatch when the trout’s metabolism is near its peak and the trout
don’t waste any time eating them. The trout usually take the Light Cahill dun
imitations readily. You want usually have any trouble detecting the take.
The Light Cahill mayflies hatch in the slow to moderate that’s immediately
adjacent to their normal fast water habitat in the runs and riffles. Most of the time
the duns are caught up in the current seams that develop between the fast and
slower moving water. They usually finish getting rid of their shuck to become
duns near the ends of the runs and riffles.
Presentation:
You want to start by placing the dun near the ends of the runs and riffles and
work your way upstream making up and across presentations.. You should
present the dun imitation in the current seams that concentrate emerging
mayflies. If the water has much turbulence, you will usually find the duns drifting
about the same place you see bubbles floating on the surface of the water.
Often the emergers work just as well or better than the duns but they are not
near as easy to fish and catching trout on the dun is usually much more fun.
They tend to sip emergers and crash the duns. The trout usually become well
aware the duns can escape before they can grab them.
Short upstream or slightly up and across cast work better than longer
presentations. It makes it much easier to get a drag free drift. The more line you
have on the water, the more difficult it is to get a drag free drift in the areas these
mayflies hatch. Keep your rod high and most of you fly line off the water to
prevent drag. Another advantage of the short cast is you can cover a lot of water
fast as you move upstream. Hit the most likely seams and keep moving. You will
rarely find a heavy concentration of these mayflies.
In some situations you may possibly get by with a 4X tippet but usually a 5X is
much better. Although you can use a 7 and half foot leader in fast pocket water
streams, most of the time a nine 9 long leader works better.
Copyright 2013 James Marsh
