Although fly fishers are usually thought of as fishing an imitation insect on the water surface, a rapidly growing number of anglers are discovering nymphs and nymph fishing. Widening realization that most of a trout's diet consists of under water insects and small crustaceans has helped accelerate this interest.

To entomologists, the term nymph designates the immature stage of aquatic insects that do not have complete metamorphosis between young and adult. To fisherman it has come to mean the under water state of most aquatic insects, and also small crustaceans like shrimp and sowbugs. Some nymph imitations are suggestive of both.

If you are a stream bait fisherman, nymph fishing won't seem all that different. The same undercut banks, tree roots, and water cress that you let a worm tumble under will produce good fish on nymphs when fished similarly. In fact a tenet of one school of nymphing is, "Use fuzzy flies and fish them like bait".

The dry fly fisher will probably start nymph fishing using dry fly tactics such as wading upstream, extending line by false casting and fishing the fly with a dead drift only, techniques that will need modifying if any where near the full potential of nymphing is to be realized.

Take a good look at the next trout you catch. See where its eyes are? Most wild things that must be constantly alert for predators, have eyes positioned to give vision to the rear as well as front, and trout are no exception. Their eyes are placed high and well back on each side of the head. The pupils are fixed in one position, and as there is no reason to believe their periphery vision isn't at least as good as ours, we must assume they see to the rear, to the front, and upwards all at the same time.

So stay out of the stream as much as possible. Wide turbulent rivers are one thing, but wading up the middle of an average Wisconsin trout stream will result in netting only adolescent fish and if it's a brown trout stream, every good fish wilI be put down for hours.

Be as inconspicuous as possible. Approach each fishing spot slowly and quietly. Take advantage of riffled water or other natural screens. Keep down. rawl on your hands and knees when necessary, to avoid being silhouetted against the sky. Wear clothes that blend with the foliage around you.

White hats and white shirts have no place on a trout stream. A wristwatch or anything else that might glisten should be carried in a pocket, and whenever feasible fish from a kneeling position.

Ideally the nymph fly should sink immediately, so once it is thoroughly wet, it wants to be kept that way. Mud wiped on the leader and saliva on the fly will act as wetting agents to help sink them quickly on the first cast.

Learn to extend line by shooting rather than false casting and keep back casts short. This is real important. False casting dries the fly and uses valuable time when the fly should be in the water. There is no way a trout can take the fly as it sails back and forth overhead.

The line is your bite indicator. It must float and be light colored for visibility. Watch it like a bobber for any pause or other deviation from normal, then pull immediately. If a line is dark colored, painting the first three or four feet by the leader knot orange or yellow will help. "Testors" model paint from the dime store works good for this and stays on for several trips.

The leader should be tapered and as long as you can handle easily. Nine feet is usually adequate. It's tippet must be light enough so the nymphs will move naturally in the water, but heavy enough to prevent the fly tangling on it when cast.

There is an old rule about tippets that will stand you in good stead here. Called the "Rule of Four", it states simply that dividing the fly hook size by four will give the right tippet size. For instance, a size 16 nymph divided by four will require a 4X tippet, a size 12 calls for 3X, etc.

This rule, like most, can be altered, by circumstances. A bulky fly needs a heavier tippet than a slender one, and as most nymphs aren't bulky, you can go one size lighter without tangling and probably get a more natural presentation.

Take the curls out of the leader before starting fishing. One way to do this is to pull the leader through a tightly folded piece of inner tube. A boot top will also work.

Many tackle stores carry a good assortment of nymph flies. If yours doesn't, usable ones can be made by simply trimming the wings of a conventional wet fly. Leave stubs to suggest the wing case.

Grays, greens, browns and combinations of these are good colors for nymph imitations in Wisconsin streams. As a general thing, early season flies are small and dark, mid-season larger and light colored, and late season a mixture of both.

Many nymphs have gills along their abdomens or thoraxes and fuzzy wool or fur bodies suggest this nicely. Peacock herl is another material that suggests gills and has an iridescent sheen very attractive to fish. Others are translucent between abdomen segments, which tinsel ribbing simulates well.

Fish them up, across, or down stream. Sometimes all three on the same cast. Keep them wet so they sink readily. Try to work them into areas where fish are feeding, then lift the rod tip to make the fly move towards the surface. This is probably the most effective motion you can give a nymph. Experiment with different retrieves and drifts. Be especially alert as the fly swings at the end of a down stream drift.

Usually un-weighted nymphs act more naturally, but if necessary, one or two glass beads slid on the leader ahead of the fly will help make it deeper. Split shot are usually too heavy and an abomination to cast.

Sometimes if there is no stream activity, repeated casts to the same area will suggest beginning insect activity and trigger the fish's feeding reflexes.

Authorities tell us in excess of 80 percent of the stream trout's diet consists of immature insects and crustaceans. In fishing nymphs you are offering trout something they are used to eating, and it's coming to them in the security of their under water feeding stations. If properly presented, nymphs will bring far more hits than other types of flies, and as you learn to recognize the hits, and to set the hook quickly enough you will catch more and bigger fish than you ever thought possible. Nymphs can make you an expert.