It's Sulphur Time Again!
By Al Caucci
Except for the Hendrickson hatch in the East, the Hex hatch in the Midwest,
and the Green Drake hatch in the West, I can't think of another hatch that
causes more excitement among America's fly fishers than the sulphurs.
Sulphurs have superior credentials: They're widespread from coast to coast;
they arrive at the most pleasant time of year in terms of air temperature and
river levels; their hatching and spinner activity lasts from four weeks to three
months; their numbers are prolific; and they are extremely vulnerable.
This Ephemerella super genus is responsible for all the "sulphur"
activity throughout the country-invaria and dorothea in the East and Midwest,
and infrequens and inermis in the West.
East and Midwest
The eastern and midwestern species of invaria are the first sulphurs to
appear. They are the largest of the group (9 to 10mm/size 14 hook) vs. the
dorothea (5 to 7mm/sizes 16 and 18 hook). The body color of invaria is more
creamish vs. the light to deep yellow color of the smaller dorothea. Invaria
prefer riffles and runs at the heads of pools, while the smaller dorothea are
prevalent on quiet pools and flats.
The larger invaria flies start hatching in mid May on Pennsylvania, New York
and southern Appalachian waters, as well as in northern Michigan and Wisconsin,
and they continue until early June. Activity starts a little later in New
England and the Upper Peninsula of Michigan. The best action takes place on
cloudy and rainy days.
The smaller dorotheas are primarily a June evening hatch in the East and
Midwest, although they will start in late May if the weather turns warm. Early
on, the hatching and spinnerfalls may get the trout going as early as 7:00 P.M.,
but as the hatch continues, it starts progressively later until the heavy
hatches and spinnerfalls occur at dusk or after dark. Proper size and pattern
type (dun, emerger or spinner, as well as nymphs in the surface film) become
critical to success as the trout feed steadily and selectively.
On rivers with abundant hatches and spinnerfalls, selectivity will be the
rule rather than the exception. On the Upper Delaware tailwater system, the
dorothea activity starts at the end of May and continues well into August.
The small, pale mayflies of Ephemerella infrequens and E. inermis are the
western counterparts of the eastern sulphurs. These "pale morning
duns" are the staples on the great western rivers like the Big Horn,
Henry's Fork, Silver Creek and Deschutes.
Like their eastern cousins, PMDs have the same hatching and body
characteristics and occupy the same type habitat niche. The infrequens nymph is
8mm (size 16 hook), while inermis is 5 to 6mm (sizes 18 & 20). The duns
resemble the eastern sulphurs, except their yellowish bodies have an olive cast,
and the wings are pale gray with a hint of yellow.
Western emergence dates are not conveniently predictable, due to differences
in altitude, geo-thermal activity and subterranean springheads. For the most
part, westerners can look for them after the runoff, when water temperatures
reach approximately 55 degrees F. July is usually the best month for hatching.
I use Comparaduns if the fish are feeding on the duns. Parachutes also work
if tied in the proper size and color, although they are less durable. When the
trout are on emergers, I like the Compara-emerger with trailing shuck and the
CDC emerger. If they are sipping spinners, use flush floating spinner patterns
in the correct size and color. Compara-spinners have hackled wings clipped top
and bottom. Poly or Z-lon winged spinners are also very effective.
Trout key on the sulphurs' most vulnerable aspects. Large fish usually wait
until the hatch is well underway before beginning to feed, but they soon settle
into a steady feeding pattern, selecting only the most vulnerable stages:
emergers transitioning to duns, crippled duns riding the surface, and spinners
lying motionless in the surface film.
Although frustrating at times to many anglers, this is the way of wild and
holdover trout. And what a wonderful challenge it is to solve the puzzle and
hook a large, persnickety trout during the sulphur hatch!