Salmon Fly or Giant Salmonfly
Introduction
One
of the most legendary and elusive of all western hatches, the Pteronarcys californica (pronounced
ter-a''nar'sus cal-i-for-ni-ca) or Salmonfly is unmatched for large
trout rising to dry flies. This hatch occurs in our area on the Yellowstone
River, Boulder
River, Madison
River when they start receding
from peak run-off. This can occur anytime from mid June to early
July. This is often a very hit or miss event and is very difficult
to plan a Montana fly fishing vacation around. The adults can move
very quickly upstream if the weather is warm or linger for several
days if cooler weather is prevalent. It's always best to start fishing
on a warm day just above where you saw the adult from the day before.
Nymph Stage
All stone flies have an incomplete life cycle meaning there are only three stages of development egg, nymph and adult. In the nymph stage the Salmonfly can live for between 2 and 4 years developing underneath the waters surface. As nymphs they feed on stream debris and drifting detritus. Stonefly nymphs need highly oxygenated, clean water and spend much of their time underneath rocks located close to fast riffled water. If swept off a rock the salmonfly nymphs are terrible swimmers and can only hope to find solid ground before an observant trout picks them out of the drift as an easy meal.
Emergence to Adult
As
the time of emergence draws closer the nymphs begin to congregate
towards the banks of the river or stream. Turning over a few rocks
along the banks will reveal numerous insects underneath. During the
early morning hours the nymphs will then crawl out of the river and
onto trees or rocks where they shed their exoskeleton. They will
then dry their wings and begin mating. As new adults they are very
clumsy and often fall into the river becoming a quick meal for hungry
trout.
Adults & Egg Layers
Once their wings dry out they begin to mate. After mating the female
lays her eggs by hovering over the water or bouncing on the water
to drop the eggs from her abdomen. Adult females can be up to 2.5
inches long and are terribly clumsy fliers. Often during peak hatches
it's a good idea to fish a large Salmon Fly dry pattern followed
by a slightly submerged pattern. Trout on pressured waters may tend
to eat the drowned pattern more readily than the dry fly imitation.