Copyright 2015 James Marsh
Hatches and Trout Flies for Twentymile Creek (GSMNP) North
We have looked at a few samples of the insect larvae in Twentymile Creek and it appears to
be the same as most other streams. The only thing we noticed was more caddisflies than we
would normally find. The area we tested was not over a mile from the lake it drains into and
that may possible have some bearing on it. The number of cased caddis seemed normal but
the net spinners seemed far more plentiful than normal.
The first insects to hatch on Twentymile Creek should be the little Winter Stoneflies.
Imitations of the nymph work good during the cold Winter. About the time these stop
hatching you will see the Little Brown Stoneflies start to hatch. They will last until the end of
April. These are actually in the same family of stoneflies but they are slightly different colors.
Blue-winged Olive are the most consistent hatch throughout the year in the Smokies. You
will start to see some hatches about the middle of February and they will continue off and on
throughout the entire year. These include the baetis species along with the Eastern BWOs,
Little BWOs and Small BWOs consisting of about 15 different species, some of which are
bi-brooded. The little Blue Quills will start to hatch about the middle of February and last
into the first of April. They are usually very large hatches that are very consistent. About the
same time you will begin to see the Quill Gordons. They hatch until as late as the first week
of April in the higher elevations.
Mid February will also bring about one of the largest caddisfly hatches of the year - the Little
Black Caddis or Brachcentrus species. This hatch is always very consistent. We have
caught more trout from this hatch than we have from the Quill Gordons during the last few
The Hendricksons start hatching near the last week of March. They are short lived, hatching
for only about a month to six weeks at the most. It is moderate and only occurs in certain
locations. I doubt there are a lot of any of the crawler mayflies in Twentymile Creek. There
are few areas of moderately flowing water and almost no large pools.
Around the middle of April, March Browns will begin to hatch. These mayflies are just about
everywhere you fish but they hatch inconsistently until around the first week of June. Much
more consistent are the Light Cahills. They start about a week or two after the March Browns
and last as long as three weeks, depending on the elevation. There are probably plenty of
all the clinger mayflies in Twentymile Creek. It water is perfectly suited for them.
The middle of April will bring about a hatch of the Short-horned Sedges. These are very
small black caddisflies that are quite abundant. About the same time you should notice the
first hatches of the Green Sedges. They hatch everywhere there is fast water for over two
months but never in large quantities. At the same time the first hatches of Cinnamon Caddis.
These caddisflies were very abundant in the lower section of Twentymile Creek. That is not
typical of the Smokies.
Around the second week of May, the Eastern Pale Evening Duns will start hatching. Most
anglers call these Sulphurs but the true Sulphurs will not start to hatch for another couple of
weeks. Both hatches last about a month but are very sparse.
The first of May the Giant Black Stoneflies will start hatching. These hatch at night and
deposit their eggs at night. Nymphs work well in the late afternoons. The Little Yellow
Stoneflies, called Yellow Sallies and one of the Smokies best hatches, will start around the
first of May and last until mid July. Another hatch also called Yellow Sallies, but different
species, starts again about September and last for about six weeks.
The Golden Stoneflies start hatching around the first of June and last about five weeks. The
Little Green Stoneflies start about the last week of May and last until July. These are sparse
hatches, but stoneflies in general are very important hatches in the small streams of Great
Smoky Mountains National Park.
The last week of June through the month of August you will find some Cream Cahills. These
are sparse but important at that time of year. By the middle of August hatches of Little Yellow
Quills will start to occur mostly in the higher elevations. This is a very good hatch that last
until the end of October. By the middle of August, hatches of Mahogany Duns will begin to
occur. This hatch last for as long as two months depending on the elevation.
Also by the middle of August you should start seeing some Needle Stoneflies. These hatch
in fairly large numbers until as late as November, especially in the higher elevations. Many
anglers take them for caddisflies which they resemble in flight. From the middle of May until
the middle of November, a long period of time, you will find hatches of Slate Drakes
occurring. These mayflies hatch out of the water but never in large quantities. Imitations of
the nymphs and spinners can be important.
The Great Autumn Brown Sedges, start hatching by the first of October and last into the first
of December. We found a huge number of their larvae in Twentymile Creek. During the
month of June, grasshoppers, beetles, ants and inch worms, all terrestrial insects, become
important food items for the trout. There are few hatches occurring, so most anglers start
using imitations of these terrestrials. The inch worms, or moth larvae, are especially
important due to the large numbers of them in the forest of the park.
In addition to the terrestrial and aquatic insects, theres a lot of other food for the trout. Small
Crayfish is one of those items. The brown trout are especially fond of them. Another one is
Sculpin. These small fish are abundant in most of the stream. Imitations of them can be very
effective. The Black Nose Dace is another baitfish that is important. Streamers imitating
these and other minnows work great especially when the water is slightly off color.
I didn't mention it in the aquatic insect part above, but midges are abundant throughout the
park. They can be very important when the water is cold and nothing else is hatching.
Imitations of the larva and pupa will catch trout anytime of the year.
Craneflies are everywhere water exist in the park. The larvae and adults are important
insects to imitate. Hellgrammites, or the larva stage of the Dobsonfly, is another abundant
insect that is in many of the park's streams.
We recommend our "Perfect Fly" imitations. They are the best, most effective flies you can
purchase and use anywhere trout exist. They have been tested and proven to work great in
all the streams in the Smokies. Please give them a try if you haven't alr\eady done so. You'll
be glad you did.
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