It was almost unbelievable that there was a blizzard on some of our local trout streams this past week. This blizzard was not typical of winter, but it was a blizzard of white mayflies. By the tens of thousands, they emerged from certain streams in Waupaca County and swirled in cyclonic formations reminiscent of murmuring starlings.
The mayflies, in a dense swarm extending a considerable distance, surged upstream just above the stream then in a pivoting turn swooped down low over the stream and surged back downstream. Their whiteness and wind-driven like flight behavior likens the event to that of a blizzard of snowflakes swirling about.
In an attempt to immerse myself in the magic of the moment, I stood in their midst feeling the brush of wings and errant impact of their bodies as they attempted to maneuver around me. It was an evening when nature displayed a unique feature of our trout streams.
This hatch was uniquely choreographed on a temporal scale. The early spinners appeared in the air about 8:05pm, by 8:25 there were hundreds on the wing in zig-zag flight over the stream, at 8:40 many thousands filled the air in large murmuring formations until 9:15. Then more suddenly than when the hatch appeared, only a few remained in flight by 9:20 as darkness closed in and the white mayflies vanished.
The performance had reached its conclusion and it was during these 90 minutes that the adult life of the white mayfly played out. Their purpose was simple and important to trout streams. It was the mating sequence of behaviors key to the survival of the white mayfly. They mate while in flight and scatter eggs across the stream surface which in turn tumble to the stream bottom and lodge there in dormancy. In late spring eggs hatch, larvae appear and grow over a period of four months in preparation to transform into adults that live their 90 minutes as an aerial form.
For fishers of trout, this is one of the most convenient hatches to fish of the season. Especially for those with a daily work schedule, as there is time for dinner before fishing and adequate time to return home after dark. The downside of this hatch is that some rivers in which white mayfly (Ephoron leukon) live reach mid-summer temperatures that exceed the thermal tolerance of trout. Therefore a great hatch can be underway and no trout are present to join the feast. Instead trout have moved to thermal refuges in spring fed tributaries or remain deep in spring holes within the rivers.
When rivers are cold enough trout abandon their shyness and boldly cruise the surface in a smorgasbord of culinary delight, that always gets the attention of fishers.
If you plan to fish this hatch, seek mid-size rivers with a bottom comprised of a gravelly sand mixture. The larvae stage of this mayfly burrows into the stream bottom much like the Brown Drake larvae that also prefer this stream bottom type. So, if you are a fisher of the late May Brown Drake hatch, the July / August white mayfly hatch will emerge from the same streams that you have familiarity.
The White Mayfly hatch is the last major mayfly hatch of the season. If you are unacquainted with fishing the Central Region of Wisconsin, the local DNR Staff can direct to many worthwhile fishing locations.
