Blue-winged Olives - Nymphs
.............................Fly Fishing Yellowstone National Park

The Blue-winged Olive nymphs are little swimming nymphs. Most anglers pay little
attention to them. They do not fish the Blue-winged Olive hatch until the duns start
appearing on the surface. There is nothing wrong with that as long as you can catch
trout prior to the start of the hatch. At the time of the season these little mayflies begin
to hatch, and that is prior to the season starting on many streams in the park, there is
not much else happening in the way of hatches. There may be some Little Black Caddis
hatching or the "Mothers Day Hatch" may not have ended but not much of anything else
is hatching when the season first opens. Of course, it may be such that the Firehole
River may be the only stream that is fishable when the season first opens. This
depends on the runoff. What I am getting to is that the Blue-winged Olive nymphs may
be one of the prime insects the trout are feeding on at that time.
There are a few specific imitations of the Blue-winged Olive nymphs but most of the time
trout can be taken on the common Pheasant Tail nymph. It imitates the little nymphs
quite well. Getting the size of the fly correct is important. They are normally a hook size
18 or 20 but they vary considerably from stream to stream and depending on the time
of the season. They may well be a size 22 or 24 during the second hatch in early
The difference in a hook size 18 and 20 is more than most anglers
, so don't think the difference is unimportant.
The nymphs are slim, narrow nymphs that look and act much like small minnows. They
can dart around in the water much like a minnow. They can also cling tightly to rocks
and the stems of plants when they feed in current. They use an up and down motion of
their abdomen and tail to swim.
The nymphs emerge in the surface skim but the trout will eat them well before they
emerge and below the surface as they rise to the surface to hatch. If the water is very
cold, in the low forties for example, it may be the only way the trout will eat them. They
may not take the emergers on the surface.
One method of fishing the nymph is to use a small strike indicator placed about 16 to 20
inches above the fly. You can use a larger dry fly to suspend the tiny nymph imitations if
you prefer. You can also fish them without an indicator. That is the way I prefer to fish
them. I usually add a small amount of non-toxic weight a few inches above the fly. I use
both an up and across cast and a down and across cast depending on the type of
water I am fishing. As a general rule, in the rough pocket water, use the up and across
cast placed at the end of the current seams. In the smooth flowing water, use a down
and across cast.
The early season hatches (
baetis tricaudatus) usually starts as early as noon. They
can hatch until 4:00 or 5:00 PM. It is a good idea to fish a nymph imitation in the
mornings prior to the hatch. In fact, it is often a good idea to fish the nymph imitation
during the time they are hatching but we will get into that in the next article.

Coming Up Next:
Blue-winged Olive - Emergers

Copyright 2008 James Marsh