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The Clinger Mayflies

Next fishing trip, indulge your wild side and spend time snorkeling through whitewater. It's cheap, it's easy, and probably no more dangerous than base jumping.

Grab a mask and snorkel then find a stretch of calm, friendly river just downstream of a rockin' bit of white water. Start at the bottom of the rapid and claw your way upstream in about two feet of water. You want to be deep enough to experience the river but shallow enough to breath from your snorkel while clinging to the streambed. Only after you've become personally aquainted with the techniques of moving through turbulent water and experienced a near drowning or two will you want to try snorkeling downstream through big white water.

There are many advantages to clawing upstream rather than gliding with the current. First of all it's great exercise and will keep you warm in the chilly water. Second, your silt plume will be trailing rather than enveloping you. Third, you retain absolute control over your progress; drifting with the current too often speeds you past cool stuff and sometimes the hydraulics will playfully stuff you under a log jam or into an undercut bank. Fourth, and most important of all, clawing upcurrent allows you to become one with the mayfly nymphs.

Stop trying to survive long enough to wrap your arms around a boulder and rest. Take a couple of slow deep breaths through the snorkel (clear as much water as possible first) and relax. Enjoy the surge of the current as it massages your shoulders, listen to the clack of cobbles being bounced towards the ocean, and watch as the water slides above you like quicksilver taffy. Within a few seconds the terror will subside and you'll be overcome by a sense of peace and tranquility as you realize what an alien, yet truly perfect, world you have entered. The bliss might also be due to an endorphin rush or advanced hypothermia.

Now, look at that boulder you're clinging to. Rest your nose on it so your field of vision is skimming right over the top of the rock. You will notice that the boulder is coated with zillions of thread-like green stalks that wave and waft gracefully in the current. It will undoubtedly remind you of an aquatic chia pet. These green hairs are the filamentous algae (one of the periphyton) that form the foundation of the aquatic food chain. Look closer at these periphyton and you'll notice something truly remarkable: it is actually only the tips of the algae that are moving with the current. In a world where your every effort is dedicated to hanging on to that rock, these tiny weeds are as unruffled as if they were relaxing in a hot tub.

In even the most tumultuous waters, there is a zone right along the streambed called the boundary layer where current ceases to exist. The friction exerted by the rocks, sticks, and old truck tires protruding from the river's floor slows the water to a virtual stop. The water in this zone diffuses with the moving water above it rather than mixing through turbulence. Compared with life in the main flow, existence in the boundary layer is a walk in the park.

There is a cadre of mayfly nymphs who have chosen to take up residence in this park. These nymphs are flattened to best take advantage of the thin calm zone. Some are hydrodynamically shaped so that the current above them actually helps press them against their bouldery domain.

The legs of these nymphs are broad and strong and splay out to the sides for maximal gripping force. The gills are adapted to press against the rock and in some nymphs these gills can even cup to create suction against the substrate (some entomologists aren't quite convinced this is so, but I'll toss my hat in with the group that does).

All of these nymphs have eyes on top of their heads rather than to the front like most. The bulging eyes create a distinctly fat face profile and any nymph you might encounter whose head is wider than the rest of the body belongs to the family of mayflies known as clingers. Even as duns and spinners, the clingers retain the distinctive shovel faced profile. In the lexicon of aquatic entomologists, all clingers are members of the Heptageniidae family.

A few years ago the Western Heptageniidae family was split into eight genera. Most of these splits were based on minute differences in the nymphs and are of little value to the angler and even less value to the trout. In the interest of simplicity, we're going to pretend the splits did not take place and we'll discuss what used to be the four important Genera of our region: the Epeorus, Cinygmula, Rhithrogenia and Heptagenia.

It is easy to tell the Heptageniidae nymphs apart. Remember, all Heptageniidae have heads that are wider than the rest of the body. If the nymph has two tails it is an Epeorus. Just that alone should get rid of half your collection. Everything else will have three tails.

Look down on the bug and if it has little points jutting out from its cheeks it's a Cinygmula (or the smaller, much rarer Cinygma but just pretend it's a Cinygmula).

If the nymph has three tails and no pointy cheeks, flip it on its back (it won't like this but ignore its feeble protest). If the gills do NOT overlap it is likely a Heptagenia and if they DO overlap it is probably a Rhithrogenia (note the disclaimers "probably" and "likely". There ARE exceptions but for our purposes these rules are good enough).

Of all the Heptageniidae, the Epeorus is by far and away the most important member for Pacific State's anglers. In Sierra waters, Epeorus outnumber all other Heptageniidae combined. Epeorus (and the new genus Ironodes which was split from the Epeorus) nymphs live in the fastest sections of river. Because Epeorus nymphs are such tenacious clingers and don't drift, I rather doubt they are very common trout fare; however, so many famous anglers have made such a to-do describing Epeorus nymphal imitations, I won't go so far as to categorically state they are unimportant.

I will state that Epeorus emergers are hugely important to trout and largely misunderstood by trout anglers. Unlike most mayflies which emerge on top of the water after the nymph has ascended to the surface, Epeorus duns crawl out of their nymphal exoskeleton while the nymph is still clinging to the river bed boulders. In some instances the act of emergence will loosen the nymph's grip on the riverbed and emergence takes place within the water column.

The freshly emerged dun carries a pocket of carbon dioxide within its crumpled wings and the buoyant gas helps the dun ascend through the water column. Once on the surface, the dun's wings dry and harden and the insect flies away. From an underwater vantage, the ascending Epeorus dun looks nothing less than a dark blob tangled in dangling legs and shimmering wings. A softhackle fly with a peacock herl body and a partridge wing is an excellent imitation, especially if it is treated with a dry powder floatant to help it retain a shiny pocket of air.

High stick this pattern with a split shot heavy enough to sink the air laden fly to the riverbed. At the end of the drift allow the line to tighten and swing the fly towards the surface like a naturally ascending emerger.

The Rhithrogenia, commonly known as a March Brown, inhabits the same turbulent habitat as the Epeorus and shares the underwater emerging trait. That same partridge and peacock softhackle works equally well for both bugs. Like the Epeorus, the Rhithrogenia will often spend long minutes drifting about the surface while it's wings dry and the dun imitation can be important.

As the name might suggest, March Browns are typically found emerging in the spring. About the time the Rithrogenia are finished emerging in early June, the Epeorus launch into action and one can expect to find them appearing throughout the summer months.

I like a low silhouette parachute dun pattern with the hackle wrapped around a post of white calf's tail stacked against a post of black calf's tail. This bi-visible wing stands out well against the alternating dark and flashy turbulent waters from which the Rhithrogenia emerges (to see a color scan and recipe of the bi-visible dun click onto bv_dun.htm).

Cinygmula and Heptagenia (as well as Nixe and Leucrocuta which used to be Heptagenias but were recently give genus status of their own) emerge in the more traditional fashion. These clingers dwell in quieter reaches of freestone streams where their nymphs swim to the surface and emergence commences in the film. Humpies make an excellent emerger imitation because their buoyant deer hair shell floats these guys well in the bouncy water and the moose hair tail penetrates the water to somewhat resemble a slipping exoskeleton.

Next time you visit clinger country be sure to carry a pocket full of softhackles, bivisible duns, and humpies. Oh yeah, and don't forget your mask and snorkel.