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Mayflies
Mayflies can be found emerging every month
of the year in the Yellowstone area. They are particularly abundant from
May through October and are an important food source for trout during
this time period. Mayflies are responsible for many of the great fly fishing
opportunities that arise during the season, and a knowledge of their habits
is invaluable for an angler.
Mayflies inhabit every trout stream and
the number of species a stream can hold is often amazing. Our friend
Dan Gustafson has found over sixty species on the Gallatin River alone,
a sign of remarkable diversity in habitat. Of course not all rivers
support so many species, and not all species are important to fly fishermen.
Some mayflies are not abundant enough to warrant individual concern,
while other species are so closely related in behavior that they can
be considered synonymous by fishermen. Other mayflies are simply not
available to trout in quantities large enough to require any attention
from fishermen.
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"The Essenstials for
Planning your
Trip to Yellowstone Park"
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The species we discuss are responsible
for virtually all of a Yellowstone angler's mayfly fishing. The list
is actually quite short, and if you do not fish certain rivers or at
certain times of the year, the list shrinks even more.
While each species has its own peculiarities,
most demonstrate a preference for similar emergence and egglaying conditions.
Knowing when the best mayfly activity will occur is as important as
knowing the individual traits of a given species.
The heaviest mayfly emergences generally
take place in overcast, cool weather. Misting rain or snow showers are
ideal and stir the blood of all fly fishermen aware of this fact.
Though we can find no substantiation
for this theory among professional entomologists, every experienced
angler we know is in agreement on this point. Entomologists tell us
that mayflies may actually prefer warm, dry conditions, and that they
hatch just as abundantly on those kinds of days. We've been told cool
weather simply concentrates the emergence over a short time period,
and that during warm, dry days just as many mayflies emerge but do so
by trickling off over longer periods.
We have trouble accepting that theory
because it runs counter to years of observation by so many people. While
inclement weather is not a strict requirement for good hatches (we have
all seen great emergences on nice days), there is no doubt in our minds
that many more flies come off when the weather is bad.
Of one thing we are sure: the
best fishing during mayfly hatches is definitely on days when
the weather is poor. If not because there are more mayflies, then certainly
because they ride the water longer in cool weather, and suffer more
emergence defects. Both these factors give the fish a better chance
to feed on them. Too, trout in general (and browns specifically) seem
to feel more comfortable feeding under overcast sides. This makes approaching
and casting to them easier.
Of the mayfly spinners important to fishermen,
all need moderately warm, calm conditions to lay their eggs. Wind stronger
than a slight breeze, cold temperatures, or any precipitation precludes
the spinners from reaching the water. Attention to the weather then,
as well as learning the habits of the prevailing mayflies, can be very
important to successfully fishing Yellowstone mayfly activity.
Mayflies are most vulnerable and available to trout while hatching and
during egg laying and subsequent spinner falls.
Hatches
Baetis
(Blue-Winged Olives, or BWOs) emerge best from I I A.M. to 4 P.M.
on overcast, rainy, or snowy days. The cooler the day, the later the
hatch.
Rhithrogena
spinners are sometimes important on calm, warm evenings during July
and August.
Pale Morning Duns
(PMDs) generally emerge at the most comfortable time of day: noon
to I P.M. on snowy days; 9 to 11 A.M. on sunny, warm days. Spinner
falls are best on cairn, warm mornings, 9 to 11 A.M., and ag?in during
the evening, 7 to 10 P.M.
Green Drakes
emerge from 10 A.M. to I P.M. Fall Green Drakes come off from I to
4 P.M. Spinner falls (seldom encountered) occur from 7 to 9 A.M.
Brown Drakes
hatch from 71010 P.M.; spinner falls coincide with emergences.
Flavs emerge on clear days from
8 to 9 P.M. In cloudy, rainy conditions look for them from I P.M.
on. Spinner falls occur from 7 to 9 p.m.
Gray Drakes on Slough Creek
emerge sporadically all day long, beginning as early as 8 A.M. Spinner
activity is better coordinated and goes from 9 A.M. until noon. On
the Yellowstone River, spinner falls occur twice each day, 8 to 10
A.M. and 7 to 9 P.M.
Callibaetis duns emerge
on lakes from 10 A.M. to 2 P.M.; spinner falls occur from 11 A.M.
to 3 p.m.
Tricorythodesshow on
the Madison River between 10 A.M. and noon; spinners are more important
than duns.
Pink Ladies hatch from
4 to 7 P.M.
Attenella margarita
duns and spinners can appear together from 9 to 11 A.M. Spinners
may fall on warm, calm evenings as well.
Serratella tibialis
duns come off between II A.M. and 3 P.M., with spinner falls from
7 to 9 P.M.
Heptagenia
duns, when found, emerge between I and 5 P.M. Spinners fall best on
warm, calm evenings.
Caddis
emerge best on warm, calm evenings. Egg-laying activity usually occurs
at the same time. However, in their peak periods caddis may also be
found laying eggs in the morning. Trout recognize both emerging and
egg-laying periods and feed best during these two events. There are
two important exceptions to this:
Lepidostoma
on the Gibbon River often emerge during the early afternoon on cloudy
days.
Hesperophylax
caddis on the Yellowstone River usually
emerge from 8 to 9 A.M.
Stoneflies,
such as the Salmonfly and Golden Stonefly, have their
strongest egg-laying periods on warm, windy, sunny days from 10 A.M.
to 6 P.M. These clumsy fliers are most available to trout when they
bounce on the water while depositing their eggs.
Little Yellow Stones lay eggs
in the late afternoon and early evening, 3 to 8 P.M.
Damselflies prefer warm, sunny
mornings and afternoons, 10 A.M. to 3 P.M. Look for migrating nymphs
and newly hatched adults along the shoreline.
Midges are important throughout
the Park. Be prepared to fish midges at any time of day, on Midge
any water.
Baetis
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| The fishing season has fully arrived
when the first of these mayflies are seen drifting the currents
of the Madison River. Their emergences herald the arrival of spring,
along with the migrating antelope and newly hatched goslings that
frequent the river bottom below Quake Lake. Runoff is still several
weeks away, and the trout feed steadily on the tiny duns in the
low, clear water.
Baetis tricaudatus (Bee'-tiss
try-caw-day'-tuss) is one of two Baetis species found
here that are important to fishermen. The other is Baetis
punctiventris, which is covered in the following chapter.
Baetis tricaudatus inhabits every trout stream in the
Yellowstone area and is often the most abundant mayfly in a
given stream. Depending on the river, emergences can occur during
any month, but typically there are two peaks: May through June,
and September through October. Baetis are small mayflies,
but their emergences are usually so concentrated that even large
fish can feed efficiently on them.
There is extensive variation
in the appearance and size of B. tricaudatus, depending
on the river and the time of year they emerge. Their size can
run from #16 to #24, an exceptional range exhibited by no other
mayfly in the area. Body color of the nymphs and duns varies
from cream to olive to gray to brown, as well as all shades
in between. Even within a given emergence there can be considerable
variation in color (and occasionally size).
But there are some common features
among Baetis tricaudatus. The nymphs all have the same
streamlined body shape and three tails. They are superb swimmers,
and move quickly through the water in short, rapid bursts.
Baetis tricaudatus
duns have two tails, slender bodies, and tiny hind wings. The
hind wings are so tiny in fact, that they are usually visible
only with magnification.
The spinners of B. tricaudatus
are rarely seen and their fate is somewhat unclear. We know
that at least one strategy the females use for egglaying is
to crawl under the water on rocks, logs, etc. to deposit their
eggs. While we have caught fish while blind fishing with wet
spinner imitations, we have never encountered a situation where
they were required. The spinners have clear wings, two tails,
and body colors ranging from brown to an opaque gray.
Emergences of Baetis
tricaudatus generally take place in afternoon; 1:00 p.m.
to 4:00 p.m. is the usual time frame. Weather plays a big role
in determining the length and intensity of an emergence. The
heaviest emergences occur in cool, overcast conditions. Light
rain or snow, common here in the spring and fall, almost guarantee
a good hatch. Look for short, sporadic hatches when the weather
is sunny and warm.
Baetis
duns emerge from their nymphal shucks at the surface. During
a sparse emergence, trout will sometimes feed on the fully emerged
duns, but it is more common to find them taking nymphs and crippled
duns in the surface film. In a heavy emergence, the fish will
concentrate almost exclusively on the nymphs, porpoising and
tailing as they pick off the nymphs just before they reach the
surface film.
Though trout, especially the
larger fish, prefer nymphs, it is not always necessary to use
a nymph pattern. On the Firehole, Madison, Yellowstone, and
Slough Creek in Yellowstone Park, trout will take dun and emerging
dun patterns readily. On the Henry's Fork and Madison below
Quake Lake, the largest fish invariably must be taken with nymph
patterns. Smaller fish on these rivers will take adult patterns,
but the big ones rarely sip even a natural dun from the surface.
Our tactics on the Madison and
Gallatin, because of their pocketwater nature, are different
than those we use on the other rivers. On the Madison and Gallatin
we approach rising fish from directly below them. We often wade
within fifteen feet of the fish, both to eliminate as many currents
as possible between us and the fish, which reduces drag, and
to improve our casting accuracy. During heavy emergences, which
are common with Baetis, trout lock tightly into narrow
feeding lanes. Getting close to the fish helps us consistently
cast our flies in these narrow lanes. Then too, the wind usually
blows stiffly during a Baetis emergence, and a close
approach helps defeat the effect of wind on our casts.
If we are using a floating fly,
such as a Sparkle Dun, it is much easier to see if the cast
is kept short. When nymph fishing to trout rolling in the current
seams, short upstream casts help us manage the inevitable drag
that quickly takes over in so many pockets. We use unweighted
nymphs, so they drift in the film at the same level the trout
are feeding at. Sometimes we see the take as a fish rolls over
the fly; other times the line simply goes taut.
Oddly enough, with a tiny Baetis
nymph it is not always necessary to strike quickly when a fish
takes. If a trout takes your fly and hooks himself, he will
often continue feeding as long as you apply no pressure to him.
We have waited a full minute before pressuring a fish that took
our nymph, all the while watching him feed as if nothing had
happened.
On rivers like the Firehole,
Yellowstone, Slough Creek or the Henry's Fork, we approach the
fish from the side and slightly upstream. These rivers don't
allow you to get quite as close to the fish as, say, on the
Madison. This, plus intricate surface currents, make drag a
major problem, and it is best handled by casting across and
downstream to the fish.
Baetis tricaudatus
emergences can be extremely heavy, so much so that it is often
difficult to compete with the naturals. You can do everything
right, and still not catch fish, simply because of the competition
your fly faces. It is important to single out one trout and
concentrate on him; flock shooting, while tempting, is usually
a fruitless tactic. It can also help to make short, quick presentations.
That is, try to put your fly a foot above the trout and not
let it drift more than a foot or two past him if he does not
take. Short, accurate drifts, repeated quickly, increase the
chance that your fly will be selected.
The fly patterns we fish with
reflect the trout's preference for nymphs and impaired duns.
Pheasant Tail nymphs, Sparkle Duns, Baetis Emergers,
and Biplanes are among our favorite patterns. As we noted earlier,
Baetis exhibit considerable variation in size. Much of
this variation is seasonal, and our fly size changes accordingly.
Spring Baetis emergences contain the largest individuals;
size #16 is possible, but most will be size #18 and #20. Fall
emergences contain individuals that range from size #20 to #24.
Our most commonly used fly size is #18 in the spring, in the
fall #22.
Despite the wide color range
of the naturals, we tie our imitations (except the Pheasant
Tail) with only grayish-olive bodies. We do not consider the
body color to be a critical factor in the success of a given
Bach's pattern, and a grayish-olive is representative of many
of our Bach's populations.
Selected emergences:
- Firehole: April 10 - July
4, September 1 - November 7
- Madison (YNP): April 10 -
July 8
- Madison: May I - June 7, September
I - October 10
- Henry's Fork: April - November
- Yellowstone: August - October
- Slough Creek: July - October
- Gallatin: May - October
Pale Morning Dun
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| The Pale Morning Dun is
arguably the single most important insect to fly fishermen
in the Yellowstone area. Pale
Morning Duns are certainly
the most important mayfly; they inhabit every trout
stream and are the major hatch on most. Each
phase of their life cycle is fed upon heavily by trout,
and they emerge continuously from May through August.
No other insect can make that claim. A knowledge of
Pale Morning Duns can do nothing but aid an angler fishing
the summer months.
Fishing a good Pale Morning
Dun emergence can be a profound experience. Our minds
overflow with memories of early June days spent fishing
the Firehole, while the river poured forth wave after
wave of duns. Trout often fed for hours, smallish rainbows
splashily rising in the middle of the stream as well
as big browns barely wrinkling the surface along a protected
bank. It was possible to fish leisurely, enjoying the
sheer spectacle of Yellowstone blossoming into spring.
Time was always on our side; the season was young and
many more emergences were yet to come. Days ten years
past are still fresh in the memory.
Then too, there are the
spinner falls. What can compare to a late summer evening
spent on the smooth flats of the Yellowstone? The tall,
bankside conifers shadow the river early, and a heightened
sense of anticipation prevails as the afternoon wind
drops. Without warning, fish that had been rising intermittently
suddenly develop regular, sustained rhythms. In mere
minutes the entire river comes alive as more cutthroat
join in. A glance at the surface reveals thousands of
Pale Morning spinners, and we always wonder how they
got there without our first noticing them in the air.
During the spinner fall
the trout feed for hours, paying fishermen no mind at
all, and while we often catch a few, it is never as
many as we think we should. It is impossible to leave
feeling that you've mastered the situation. Perhaps
it should be this way, for that is exactly what keeps
us coming back.
Two mayfly species make
up the Pale Morning Dun experience; Ephemerella
infrequens (Uh-fem-er-el'-la in-free'-kwens) and
Ephemerella inermis (in-er'-mis). Both
species look alike, except in size. Duns of both species
exhibit wide variations in body color. Luckily, a strict
determination of species is unnecessary since both flies
have similar behavioral patterns.
Generally speaking, E.
infrequens is the first of the two to emerge in
the season, doing so from the end of May through June.
They are larger than E. inermis', size #14 to
#16 is the common range of the nymphs and adults. Ephemerella
inermis is size #18 most often, but can be as small
as #20. Their emergence takes place from mid-June through
August.
Because the two species
look and act alike they can be treated as one-simply,
the Pale Morning Dun. The nymphs are three tailed crawlers,
and range in color from amber to brown to almost black.
Populations can reach incredible densities in good habitat;
we have seined several hundred individuals from just
a square foot of gravel bottom on the Henry's Fork.
The duns are stately
looking mayflies, with three tails, well proportioned
bodies and wings, and a body color spectrum that encompasses
everything from pastel green to bright yellow to orange
and on to a rich mahogany. Much of this variation in
color is sexually dependent. Female duns are typically
lighter and more subdued in color than the males. The
wings of all Pale Morning Duns are pale gray.
Pale Morning Dun spinners
have three tails and clear wings. The female spinners
have olive bodies, the male's are a rusty brown in color.
Each phase of the life
cycle of the Pale Morning Dun provides tremendous angling
opportunities. The nymphs are readily available as they
ascend to the surface and as they drift in the surface
film prior to shedding their shucks. Large trout frequently
feed only on the nymphs during emergence.
Then too, the successful
transformation from nymph to dun is never a given either.
Deformed and stillborn duns are common enough that trout
often feed exclusively on them, knowing full well how
vulnerable these flies are. Successfully emerged Pale
Morning Duns sometimes ride the water for long distances,
providing trout another chance to take them.
The spinner stage is
extremely important for both anglers and trout too.
Pale Morning spinners fall in the morning, evening,
or, frequently, both morning and evening.
Besides presenting so
many varying opportunities for fly fishermen and trout.
Pale Morning Dun activity is remarkably
predictable and consistent.
When they are in season and the daily weather is conducive,
you can count on their presence.
Because Pale Morning
Duns emerge from May through August it is impossible
to assign a time of day to expect them. In general they
emerge at the most comfortable time of the day. On a
snowy June day on the Firehole that means around noon
or 1:00 p.m., when the temperature peaks for the day.
A bright, hot day in July on the Henry's Fork may find
Pale Mornings emerging as early as 9:00 a.m. in an effort
to avoid the heat of the day. 11:00 a.m. is probably
most typical on a day without unusual weather circumstances-by
then the early morning chill is out of the air, and
the heat of the day is still several hours away. Emergences
can last from thirty minutes to over three hours.
Spinner falls can be
expected on calm mornings and/or evenings. Normal time
frames are between 9:00 a.m. and 11:00 a.m. and from
7:00 p.m. to 10:30 p.m. As with the emergences, there
is a tendency for the spinners to choose the most comfortable
time within the ranges we have given.
When fishing an emergence,
it is necessary to carry nymph and dun patterns. We
carry two kinds of nymph, depending on where we are
fishing. One type is tied so it can be fished subsurface,
the other is tied to float. On the Firehole and Henry's
Fork, for example, the fish often prefer to take nymphs
in the surface film, in which case we use the floating
pattern. The big, wary fish in the Madison-mostly brown
trout between sixteen and twenty inches-invariably ignore
floating flies of any kind during this hatch. They still
feed actively, but only on drifting nymphs. Situations
like this call for a subsurface pattern that sinks roughly
four to six inches. An unweighted Pheasant Tail nymph
works well.
The dun pattern we prefer
is the Sparkle Dun. This fly is a good representation
of an emerging dun, or a dun trapped in its shuck. Fish
sometimes key in on this stage and a good imitation
can make all the difference. Even when fish may be taking
fully emerged duns, we still use a Sparkle Dun. We are
convinced that trout recognize crippled or otherwise
impaired duns and, whether or not they are currently
feeding on them, almost always accept an imitation of
one.
It is difficult, but
sometimes necessary, to determine whether trout are
taking nymphs or duns. In certain holding spots fish
may see more of one than the other drifting by, and
may develop a selectivity to one stage. Watching naturals
drift over a trout and seeing them taken is obviously
the best indication of dun feeding. Noses and heads
breaking the water are another likely sign of dun feeding.
If the fish continues feeding as duns pass overhead,
think nymphs. If backs and tails, or just tails alone
are seen, nymphs are almost surely being taken.
Pale Morning Dun spinners
are best imitated with a pale . olive or rusty Sparkle
Spinner. We don't believe we have witnessed a time when
the trout preferred one color, but we still carry and
use both. Trout can be extremely tough to catch when
they lock onto spinners and we aren't ruling out the
possibility that color may be involved.
Selected emergences:
- Firehole: May 10-July
8
- Madison (YNP): May
5 - July 8
- Henry's Fork: June
I - July 30
- Madison: June 25 -
August 13
- Slough Creek: July
I - July 20
- Yellowstone River:
July 15 - September 5
Flavs
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| Along with Brown
Drakes, Flavs are the only other mayfly of importance
here that emerge in the evening. But unlike Brown
Drakes, Flavs are far more widespread and numerous;
they are one of this area's most significant summer
mayfly hatches. Flavs are a sizable mayfly, capable
of bringing up the largest fish in a river to
surface feed. Their emergences hold few secrets
too; Flav hatches are often responsible for some
of this area's easiest dry fly fishing. The name
Flav is derived from their Latin name, Drunella
flavilinea (Drew-nell'-uh flav-uh-lin-ee'-uh).
Flavs are found
in abundance on the following rivers: Henry's
Fork, Yellowstone, the Firehole, and the Madison
below Quake Lake. Depending on the river, emergences
can occur anytime from the middle of June to
the middle of August. The time of day to expect
a hatch varies considerably depending on the
weather. On sunny, warm summer days Flavs will
begin emerging around sunset or a short while
on either side. At this latitude in July that
means sometime between 8:00 p.m. and 10:00 p.m.
When weather conditions are rainy, cool, or
heavily overcast, Flavs often appear much earlier;
5:00 p.m. or 6:00 p.m. is typical, and we have
seen them emerge in good numbers as early as
3:00 p.m. Emergences last anywhere from thirty
minutes to two hours.
Inclement weather
always seems to prompt the heaviest emergences
and the best rises of fish. We look forward
to rain, wind, and cold because they almost
insure good Flav activity. Ironically, these
same conditions drive most anglers from the
stream just when they should be starting.
Last July, for
instance, we hit a brief but superb emergence
on the Madison. We had arrived at the Cliff
and Wade Lake bridge at five o'clock in the
afternoon in a light drizzle and cool breeze.
We proceeded to string our rods as several groups
of fishermen around us shed their gear and headed
home. Most of the anglers leaving had spent
the whole day on the river, and when it started
raining around dinner time, they decided to
call it quits. Those we visited with thought
we must be crazy to fish under these conditions,
but past experiences encouraged us to stick
around. After all, it was still early.
By six o'clock
the rain ceased, and another one of those infamous
eerie calms surrounded us. It felt as though
we were in the eye of a hurricane. The mountains
were still blanketed with storm clouds, and
in the early darkness we had a sense that something
big was about to happen. The air felt warmer
in the calm, and a brief moment later the river
pockets were filled with drifting Flavs. Fish
began working immediately and so did we.
We fished intensely,
for we had been in many of these situations
before and knew that rain and wind could start
again anytime, putting a damper on the hatch
and the feeding activity.
We cast to the biggest fish we saw, and our
Sparkle Duns were taken without hesitation.
Our catch included more brown trout than rainbows,
a rarity for the Madison, but one that reveals
the power of this emergence, plus early darkness,
to lure out even the normally shy, nocturnal
browns.
Flavs are sometimes
referred to as Small Western Green Drakes, a
descriptive but ungainly name. With olive bodies,
dark gray wings and three tails the duns superficially
resemble their Green Drake cousins. Flavs, however,
run from size #14 to #16. Spinners have clear
wings, a dark olive to olive brown body, and
three tails. Flav
nymphs are stocky, three tailed crawlers, and
they can be found in all shades of brown.
Flavs emerge
at the surface and fish generally feed on the
drifting duns. Finding fish concentrating on
the nymphs is rare, and we almost never use
a nymph imitation. Our favorite pattern is the
Sparkle Dun, an emerging dun imitation. Even
though Flavs are not as prone to emergence defects
as, say, Pale Morning Duns, emerger patterns
still work well.
Flav spinners
fall in the evenings and, when concentrated
alone, can stimulate good rises of fish. Flav
spinners are often overshadowed by the simultaneous
emergence of caddisflies, particularly on the
Madison and Yellowstone. Still, it is wise to
carry appropriate imitations. Flav emergences
and spinner falls are unlikely to coincide,
for when an emergence takes place on a nice,
warm evening it will probably occur after any
spinner fall has occurred. And, while inclement
weather can stimulate excellent emergences,
it will preclude any spinners from falling.
Selected emergences:
- Firehole:
June 10 - June 25
- Henry's Fork:
June 24 - July 25
- Madison: July
15 - August 10
- Yellowstone:
July 20 - August 10
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Gray Drake
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| Slough Creek lies
in the most scenic part of Yellowstone, meandering
first through small, alpine meadows, then plunging
through a tight gorge and eventually spilling
into the wide open, sagebrush covered Lamar valley.
The Beartooth Mountains cut a jagged horizon in
the distance, and the land is prime elk, buffalo,
and grizzly bear habitat. An angler's first look
at the river, however, is likely to be as uninspiring
as his first glances at the surrounding scenery
prove inspiring. It looks like anything but the
incredibly productive trout water it is.
The lower meadow
section of the river is full of long, deep,
silty, slow pools, interspersed with short riffles.
The upper meadows are mostly unbroken stretches
of slow-flowing, meandering water, with huge
depositions of glacial sand on the inside of
every corner. Scoured out, crumbling banks are
a common sight; an unfortunate testament to
the torrential runoff the whole river suffers
in June.
But the appearance
of the river belies it's productivity, for it
contains a wealth of fish and insect life. The
trout are cutthroat and rainbows, sculpin abound
in the riffles, and all variety of important
mayflies are plentiful. One of these, the Gray
Drake, is especially significant.
The Gray Drake,
Siphlonurus occidentalis (Siff-lo-nur'-us
ox-uh-den-tay'-lis), is Slough's largest mayfly,
about a size #10, and they emerge from early
July through the middle of September. Excellent
populations are also present on the Yellowstone
River, Yellowstone Lake, and the Henry's Fork
below Ashton. Siphlonurus emerges from
July through the middle of September.
Siphlonurus
nymphs are superb swimmers. Their three feathery
tails, strong abdomens, and streamlined shapes
allow them to move quickly through the water
in short bursts. Mature nymphs congregate and
emerge along shore, never really exposing themselves
to the trout, which obviously limits their significance
in fishing. Many nymphs actually crawl out of
the water onto weeds or logs to complete emergence.
Siphlonurus
occidentalis
duns are two tailed, with light gray wings and
pale olive to tan bodies. There are dark brown
rings at the rear of each body segment. As with
the nymphs, the duns are relatively insignificant.
Unless a strong wind is blowing, forcing the
duns away from the shore where they emerged,
fish can't take advantage of them. They also
have a tendency to emerge sporadically throughout
the day, never giving the trout a chance to
get tuned into them.
The spinner stage
is a different story. The morning falls are
well coordinated, with hordes of Drakes swarming
over and then falling to the water surface.
These concentrated falls give the trout every
opportunity to feed, and feed heavily they do.
Siphlonurus bring up the largest fish
to surface feed, and this activity takes place
from approximately 10:00 a.m. to 12:00 noon.
If conditions are right, there will be occasional
falls in the evening too; this is something
we see frequently on the Yellowstone.
The S. occidentalis
spinner has two tails and a tannish body with
distinctive dark brown horseshoe markings on
the underside of their abdomen. Like all spinners
the wings are clear.
Because of the
size of these mayflies, fish can be a little
shy about taking the spinners, and we always
use fine tippets and sparsely tied patterns.
The take itself is invariably slow and deliberate,
so a careful strike is essential. It is very
easy to strike too quickly, especially on the
Yellowstone and Slough Creek, where the cutthroat
trout are naturally slow takers to begin with.
Selected emergences:
- Slough Creek:
July I - September 17
- Yellowstone
River: July 18 - September 15
- Yellowstone
Lake: July Henry's Fork: late June - July
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