Emergers
by: Mike Lawson
The selectivity of the trout is a mystery that will never be completely solved. The complexities of why these fish behave the way they do has been discussed for decades, even centuries. Being the proprietor of a fly fishing shop on one of the world's most challenging dry fly rivers for twenty1 years has enabled me to listen to the theories of some of the greatest engineers of the fly fishing world. The argument goes on as to which pattern best imitates a given mayfly. The merits of no-hackles, thorax, comparaduns, cut wing duns, paraduns, etc. have been discussed in detail. Each advocate can give a very convincing argument as to why his pattern is best but these arguments will never be either won or lost. I have learned much through these discussions but my real education has been on the stream.
One of the most common mistakes anglers make when trout become selective is to randomly change patterns. Replacing a thorax with a comparadun makes very little sense since both patterns imitate the same thing, the freshly hatched dun. If the trout are feeding on the freshly emerged duns, chances are a thorax, comparadun, or any other pattern that simulates the dun will work equally as well under the same circumstances. A more practical approach is to try to better understand the life cycle of the mayfly and what happens during the emergence.
Trout become conditioned to feed on the food source that provides the greatest compensation for the least amount of effort. A freshly hatched mayfly dun will fly from the surface as soon as it gets its wings dry. If the humidity is high and the air temperature is low, the dun may drift a considerable distance before it lifts from the water. Under warm, dry conditions the dun will leave the surface almost immediately. Large trout soon learn there is much easier prey than a fluttering dun that may flee at the last second.
Almost all mayflies live for one year as nymphs in their subsurface environment. They hatch into a dun for only one reason, to mate and lay their eggs. Most of them die only one day or less after they emerge. The stage at which the winged dun pulls itself from the nymphal shuck is called the emerger. Emergers are neither nymphs or duns. Most emergers drift suspended in the surface film while the winged dun escapes the nymphal skin. During this time the mayflies are completely helpless, offering large trout an opportunity to leisurely feed while expending a minimum amount of energy.
