.............................Fly Fishing Yellowstone National Park

Giant Salmonflies (Pieronarcys californica) - Nymphs

The nymphs of the salmonfly are huge. It doesn’t take many of them to interest the trout
or to get them to feeding selectively on them. When the hatch is on, you can spot them
moving across the bottom of the stream. Like most all stoneflies, the salmonflies crawl
out on the banks and rocks to hatch into adults.
Most activity takes place during the evenings but some hatch during the day, especially
if it is late in the day or early in the morning. Overcast, rainy days usually provides good
nymph fishing but that is not a requirement. Trout can be taken to some extent all day
long on the nymphs, especially during large hatches. Trout get accustomed to seeing
them and feeding on them and seem to accept imitations presented anytime day or
The nymphs are a chocolate brown to black color. Prior to their hatching into adults, the
nymph’s stomachs turn a salmon orange color. Notice that the color of the nymphs is
almost uniform. It doesn’t take a sophisticated pattern to work. If the shape, size and
color is close, then most likely it will be effective.
The weight of your imitation is very important. It must be heavy enough to stay on the
bottom. Using added weight helps but the fly itself should be weighted at least to some
extent. Remember the non-toxic rule for the park.
You can easily find the large nymphs by picking up smaller stones on the bottom. They
are usually mixed in with other caddisfly and mayfly nymphs. Although they look like
they could bite you, they don’t.
When the salmonflies are hatching, you can always find their shucks along the banks. If
you examine the bushes along the banks of the stream you will most always be able to
find the adults. They live a relatively long time out of the water and are easy to spot due
to their large size. In fact, if the hatch is prolific the bushes will be loaded with the
The hatch moves upstream sometimes as much as three to five miles a day.  This
distance strictly depends on the changes in elevations, weather and the associated
water temperature. If the weather is stable the water temperatures are usually warmer
at lower elevations than higher elevations. As the water warms upstream, the hatch
progresses upstream. Of course a cold front can change these conditions quickly. Very
warm unseasonable weather can speed the hatch up. Those anglers that have never
fished the hatch should certainly try to catch it one season. It is a spectacular event to

Nymph Presentation:
During the hatch the trout are used to seeing the large nymphs move across the bottom
to the banks. We suggest that you walk along the banks and present the nymph
imitation very close to the bank using very short cast in an upstream direction. This way
you can cover a lot of water without spooking the fish. Make sure you bring the nymph
imitation all the way back to the bank. There isn’t much need to be casting far out into
the stream. Time is spent more productively presenting the nymph close to the banks
where the trout are obviously waiting on the nymphs to crawl out of the water.

Coming Up Next:
Giant Salmonflies (Pieronarcys californica) - Adults

Copyright 2008 James