Streams Outside of Yellowstone National Park
.............................Fly Fishing Yellowstone National Park


Henry's Fork of the Snake River Hatches - Part 2

The first and foremost aquatic insect that you should consider important at Henry's
Fork of the Snake River, as well as most anywhere else in the country, is the
Blue-winged Olive. Anglers don't want to think in those terms when they are visiting the
West to fish for trout. They want to think in terms of big flies and big hatches. While
there is nothing wrong with that, it is just a fact that the little BWOs are just as important
on the Henry's Fork as there are anywhere. There is usually a hatch going on
somewhere on the river just about anytime from March until November. Generally
speaking, there is an early season and a late season hatch of the
baetis species but
the times vary depending on the section of the river.

Many anglers don't think about fishing the Henry's Fork until mid June when the season
starts in the Harriman State Park section. That misses a ton of fly fishing action,
including the big Salmonflies. The huge stoneflies start hatching on the lower part of
the river and moves upstream. They are most prolific in the fast water or pocket water
sections of the river such as the canyon sections.

For purposes of this article I will start with the section between Aston and Chester.
Below Aston Dam, one of our favorite sections, the BWOs start hatching around the
first of March. The hatches can last through April. Since the river is feed by a lot of
springs, the water is not as cold as one may think. The salmonfly hatch will begin just
past mid May. The guides are usually very busy on this section of the river at that time.
The fishing can be fantastic.

Several species of caddisflies start hatching during the month of April and continue
throughout the rest of the year until November. The Little Black Caddis (Mother's day
hatch) usually starts around mid March to the first of April and last three or four weeks.
By mid May the Spotted Sedges start hatching. This is the most prolific species to
hatch. It will last until the first week or two in July with different species hatching at
different times. At that time the river flows are greatly affect by irrigation demands.
Shorty after the Spotted Sedges start hatching, usually two or three weeks, near the
first of June the smaller Little Sisters will begin to hatch.

In June the large Western Green Drakes will start to hatch in this section of the river
and last a couple of weeks at the most. Nearer the end of the month the smaller Flavs
or Small Western Green Drakes will hatch.

Other than the BWOs the most important species is the PMDs or Pale Morning Duns.
They hatch over a long period of time beginning in late May.

This section of the Henry's Fork has another important mayfly that starts to hatch
around the first of June - the Gray Drake. These larger mayflies hatch in the late
afternoons. The nymphs and the spinners are the most important stages of life to

Although the PMDs and a few species of caddisfies will hatch in this section of the river
throughout the summer months, the irrigation demands on the water creates a less
than ideal fly fishing situation. By the end of September the action will again pick up in
this section. October can be a great month to fish with the Blue-winged Olives being
the main species to imitate.

Copyright 2008 James Marsh     
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