My interest in fishing emergers and traditional wet flies began many years ago as I stood on the edge of a well know stream changing fly after fly while watching mayfly duns drift the length of the run I was fishing almost untouched. I remembered thinking to myself, why aren't they taking the duns, why aren't they taking my dry fly imitation, why am I only catching a few dinks? I had already added a couple of feet of smaller diameter tippet material lengthening my leader by a couple of feet. I had tried a smaller imitation of the fly that I thought was hatching, I could see fish feeding as they bulged just beneath the surface. Then it hit me like the proverbial ton of bricks, they are feeding on the mayflies as they are emerging!
An emerger is the life stage when an aquatic insect begins to either rise to the surface, crawl onto shore, or shed its skin beneath the water in preparation to hatch. The insect is most vulnerable during this transition from nymph to adult. Many insects, especially mayflies are still subsurface as they emerge. Light Cahills are one of the most prolific hatches of the Southern Appalachians. They often last for months and are found in abundance thru out the Smokies. I like to fish these type of flies on a dropper about 18" behind a dry fly imitation of the adult as an indicator. Try it sometime, even during a full blown hatch when you can actually see fish eating adults you'll be surprised at how many fish will still prefer the emerger.
Although you may actually see the Cahill duns in runs and slower water, the nymphs live in some of the faster sections of a stream. A good way to fish a tandem of a dry and emerging Cahill mayfly is to position yourself near the tail of a riffle and cast up and across stream and allow your fly to drift from the tail of the riffle into the run or pool below. Fish will often move up to the head of the run or pool as the nymphs become more active in anticipation of the hatch.
Thread: 8/0 UNI Light Cahill
Trailing shuck: Rusty Antron Yarn
Body: Light Cahill Turkey Biot
Thorax" Yellow Rabbit
Hackle: Whiting Hen Saddle