Trout fishing in our rivers and streams has been productive, despite the low flows and lack of rain. With water levels at less than half their normal volume, we are fortunate that temperatures have …
Trout fishing in our rivers and streams has been productive, despite the low flows and lack of rain. With water levels at less than half their normal volume, we are fortunate that temperatures have remained cool, and wading is easy.
A nice variety of flies are hatching, from a few remaining Hendricksons on some smaller streams, as well as Caddis flies of different sizes and shapes, to the next group of mayflies: March Browns and Gray Foxes.
While walking the dog earlier this week I noticed the Jack-In-The-Pulpit and red Trillium (Wake Robin) blooming behind our barn and plucked out the first of the wild garlic mustard plants that, although edible, are highly invasive.
These blossoms coincide with the hatching of the American March Brown mayflies (Stenonema vicarium) on our streams.
March Browns (which, despite their name, do not hatch in March here in the Catskills) are large (size #10) mayflies that appear in mid-to-late-May and are an anticipated hatch both for trout as well as trout fishers.
They are the first of the large flies to hatch during the fishing season and are relatively easy to identify due to their size, with mottled brown wings and brown markings on their legs; their wings, unlike most other mayflies, are slanted slightly back rather than being carried straight upright.
The adult winged stage is actually the briefest in their life cycle; and as with other mayflies, the Stenonema (March Browns) spend most of their lives underwater as nymphs.
These large nymphs prefer strong currents and have the ability to cling on to rocks and other stream debris. During this stage in their life cycle they have three tails.
At times the nymphs will become dislodged, especially after a heavy downpour, and are an important source of food for hungry fish. When the nymphs are mature enough to enter the next stage of their lifecycle, they will rise from the bottom substrate, making their way to the still waters along the shore several days before they are ready to emerge from their nymphal cases.
The nymphs are particularly vulnerable to predation, as they are an easy target for hungry fish from the time they swim up from the bottom of the stream to the surface, wriggling animatedly in an attempt to force open their cases, which split open at the back, either while on the water’s surface or after crawling out onto rocks or debris.
Once the fly emerges, it may use its case as a raft and will float downstream until its wings are dry. At this stage in its lifecycle it is known to fishermen as a “dun,” perhaps referring to the lackluster appearance of its wings. Interestingly, it has evolved from a three-tailed nymph to having just two tails as a dun.
Next the dun will endeavor, sometimes after several attempts, to reach a tree or bush along the stream where it will remain for up to twenty-four hours and undergo its last transformation, developing its breeding organs, and transposing to a “spinner,” with a more slender body and beautiful, clear, sail-like wings.
Spinners can fly much faster than the slower duns, traveling in an up-and-down pattern while mating, which some fly-fishers refer to as the “spinner dance.”
They are unable to eat, as they no longer have mouths after their final metamorphosis, but complete their life cycle by breeding. The male dies just after mating, while the female expires after depositing her eggs on the surface of the water.
These eggs sink down to the bottom of the stream; their sticky coating enables them to adhere to the rocks and bottom substrate. When they hatch and the nymphs emerge, they will shed their outer layers as they grow.
Unlike other species, the March Brown does not hatch at a regular or specific time, but will hatch sporadically, tending to emerge during the warmer parts of the day, usually toward noon into the evening. They are a favorite springtime hatch as they are one of the easier flies to identify, and often result in splashy rises by the trout taking them.
Fly-fishers do well during March Brown time fishing either below the surface with a March Brown nymph or above with a dry fly imitation.
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