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

Baetis tricaudatus usually start hatching before the season opens in the park. It
depends on the stream. It has a second hatch that usually occurs in September and
October. Generally, hatches in the Firehole and Madison area of the park start prior to
the hatches in most other areas of the park, especially the Northeastern section. It is
not so much the elevation of the rivers that determine this as it is the drainage. For
example, the mountains surrounding the Lamar Valley are higher and larger than the
mountains surrounding the Madison drainage. The resulting snow pack makes a big
difference in the stream water temperature and consequently, the timing of the hatches.
Hatches in the Northeast, Southeast and Southwestern sections follow the hatches in
the Madison drainage area. Gallatin River hatches always occur later than the other
Northwestern section streams due to the elevation and drainage of its headwaters. It is
a very cold stream early in the season.
Plauditus  punctiventris or Little Blue-winged Olive hatch starts about the first of
June in the Madison drainage. It starts later in most other areas of the park. Like the
tricaudatus, it has a late season hatch that usually occurs in September and October
depending on the stream. Both species of these mayflies are similar but the
punctiventris species are smaller. They are usually a hook size 22 to 24.
As I said in the previous article, trout will feed on the nymphs even after the hatch
starts. This is more common in the early season than during the late season hatches.
The colder the water, the more likely the trout will feed on the nymphs after the hatch
gets underway. I suggest fishing the nymph up until the hatch starts. After the hatch
begins, I would continue with the nymph imitation. When the trout stop taking your
nymph imitation, change to an emerger pattern. Normally, emerger imitations work great.
One problem you may encounter is that in some cases, there are so many flies
hatching, it is difficult for you to get the trout to select your imitation out of crowd of real
ones. This happens on the Madison and Firehole rather frequently. Both streams have
prolific hatches of Blue-winged Olives. In that case, you may want to concentrate on
one fish. Doing so is not a bad idea anytime. If you can time the cast and drift it over the
feeding trout just right, you will have a better chance of the trout taking your fly over the
The Blue-winged Olive hatch can drive anyone nuts. It is difficult to watch several large
trout continuously rising to mayflies when they ignore your fly. This is not a rare
occasion when the Olives are hatching in smooth water. If you are not careful, you will
find yourself changing flies too often, worrying about your leader and tippet size too
much, and pounding the water with different types of presentations.
You must make a
good presentation to fool the trout in the smooth, clear water
. You must have a
good imitation of the particular stage of the hatch the trout are focusing on.
The one problem I see most often, is that the angler is set on using a dun pattern when
the fish are much more prone to take a floating nymph or emerger pattern. Emergers
are not as easy to fish as the dun imitations, but they are usually more effective during
the hatch, especially early in the season.

Coming Up Next:
Blue-winged Olive - Duns

Copyright 2008 James Marsh