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Understanding emergers

I often get asked a lot of questions regarding trout flies. One of the questions most frequently asked is, “What are emergers?”

Simply put, the flies known as emergers represent the emergent stage of an insect. It is probably the stage in which the insect can be most vulnerable to a hungry trout. As a result, it is an extremely important stage of the insect to represent.

There are four main groups of aquatic insects of major importance to fly fishers: they are stoneflies, caddisflies, mayflies and midges.



Generally, Stoneflies do not have a significant emergence, since they crawl out of the water in their nymphal stage and emerge into adulthood on land. They are not readily available to the trout at this time, so the emergent stage of the Stonefly has little importance to the fly fisher.

The other three groups do have emergent stages. In the case of the caddisflies and midges, it is the pupal stage of the insect that most try to imitate with emergers.



In the case of the mayfly, it is when the nymph swims to the surface and escapes its nymphal case with the help of the surface tension of the water. Fishing these emergences takes place from the top down to inches from the water’s surface. In many cases, it is just like fishing a dry fly. Therefore, fly fishers love to fish imitations of these insects.

The emergent pupal stage of the caddisflies and midges occur quickly. The insects rise from the bottom with the aid of air bubbles and pop through the water’s surface pretty quickly. As a result, the fish will chase these insects with vigor. You may see trout leaping completely out of the water when they are chasing emerging caddisflies or midges.

There are a tremendous number of fly patterns to imitate this stage, and most use some form of parachute-style hackle that allows the back end of the fly to rest beneath the surface of the water. This apparently gives the impression of the insect trying to break through the meniscus.

Mayfly imitations are probably the most widely imitated emergers. This is probably because this stage of the mayfly is arguably the most vulnerable stage of any aquatic insect. This is due to the length of time it takes the emerging insect to pull itself out of its nymphal case. During this time, escape is impossible and the fish seem to feed slowly and methodically knowing that their prey is not going to fly off.

New fly fishermen can sometimes have a difficult time identifying these feeding periods. When you observe that fish appear to be feeding on top, notice whether or not the fish are creating bubbles when the are eating. The presence of air bubbles means that they have taken an adult insect on the surface.

You can also watch the adult insects, in the case of the mayfly, to see if they are being eaten. If they are floating by unmolested, then the odds are that what you are seeing are a result of the emergent stage of the insect. Emergers are probably the patterns that most anglers are most successful with during this feed period. As a result, you should carry a good supply of these flies in your vest.

If you want to know more about this stage of the insect and the fly patterns, there is a great new book on the market, “Tying Emergers,” by Jim Schollmeyer and Ted Leeson. A detailed preview of this book appears in the June 2004 issue of “California Fly Fisher” by Richard Anderson. Copies of this magazine are available locally.

Bruce Ajari, a Truckee resident, is a regular fishing columnist for the Sierra Sun and other local newspapers.


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