The Czech nymphing style is a rapid, close range method that utilizes the fast, turbulent and usually ignored water present on most trout streams. The principle of Czech nymphing is to get the flies down deep as fast as possible. For this reason, the flies used must be as slim as possible, simply a sparse covering over a lead underbody. Nothing that could slow the fly's descent should be added (excessively large legs, hackles etc). For Czech nymphing, there is no casting as suc -- only three to six feet of fly line is actually used while fishing, with only the leader in the water.
Due to the lack of casting, leader type doesn't really matter; tapered leaders are fine but most use level monofilament. Leader strength should be determined by two factors: fish size and the riverbed. When fishing deep, the riverbed will be snagged on a regular basis. Iit is helpful for both the angler's enjoyment and his wallet that the leader is of the appropriate strength to remove snagged flies without loss. A leader for Czech nymphing should be roughly a rod's length long with two droppers placed around twenty inches apart.
The difference in weight between flies and their position on the leader can also determine the effectiveness of the method. The heaviest should be placed in between the top and point fly. The reason being that the middle fly should pull those either side of it down allowing them to fish correctly along the bottom. If, however, the heavy fly is placed on the point the top dropper may not have the weight on its own to reach the bottom, thus limiting the anglers chances. When fishing it is essential to examine the flies every few casts for weed removal (if present) and for blunted hooks after any encounters with snags. If the flies are snagged excessively, alternate their weight. The flies must bounce and roll along the bottom not scour it. When fishing, the angler's eyes must never leave the tip of the fly line, takes can be either strong and violent or feather light and unnoticeable.
The fishing technique is simple but the approach is often more important. Fish are never all along the opposite bank so wading should be careful and slow. All water from the foot of the bank to the focal point of the swim should be fished. Due to the presence of three heavy flies on one leader the cast must involve nothing more than a slow deliberate upstream lob, short sharp flicks can result in a short sharp shocks. The flies should be followed by the rod tip downstream until the rod is fully extended and the flies start to rise to the surface, the cast should now be re-made and the procedure repeated. As soon as the flies hit the water watch for anything out of the ordinary, a slight slowing and hesitation of the line or a quick sharp jerk in the opposite direction of the flow. Strike on every occasion -- what may seem like a snag may be a fish.
Basic Czech nymph dressing
Notes on tying
Cut a strip of lead foil about 1.5 mm wide, apply the lead halfway round the hook bend and wind to one wraps distance from the eye, then wind over the previous layer down to two or three wraps shy of the initial start point.
Apply the thread either at the eye or a third along the underbody, when secure, tie in both the mono and the wire/tinsel and wind over towards the bend just past the lead, now wind forward 3 or 4 mm. Prepare the shell back so it's the perfect width to cover the back of the fly, cut a point in the end and tie in working backwards over the few mm that were left earlier.
Apply the chosen abdomen dubbing to the thread and wind along two thirds of the hook, now apply the thorax dubbing and wind to the eye. At this point put on a couple of whips or a half hitch to prevent the thread being knocked over the eye.
In open turns wind on the under rib up to the eye, tie in and again whip or half hitch.
Pull over the shellback and tie it in securely at the eye and whip or half hitch for security.
Take the mono rib and wind it in between the windings of the under rib. When winding over shell backs they tend to migrate over to one side of the hook as the mono is pulled around the fly, check with every winding whether this is happening and correct if necessary. Tie in the mono at the eye and whip finish.
There are many colours of shell back available but alternatively buy one colour and mark with a waterproof pen. Wipe the pen over the back of the completed fly and quickly wipe off leaving the colour in the recesses created by the mono rib. This gives a nice segmented appearance.
Check out these videos:
A Guide to Czech Nymphing (21:34)
301 Fly Tying with Greg Blessing: Colorado Guide flies, Part 1
Fy Tying with Juan Ramirez. Caddis