The Pheasant Tail, Swedish and Gray Goose nymphs are all variations of the same pattern and fished with the same technique, often called the 'Netheravon Style'. The Pheasant Tail Nymph is a generic darker nymph, the Swedish represents the Summer Mayfly nymph found in northern latitudes, while the Gray Goose represents the lighter colored nymphs such as the Pale Wateries and Blue Winged Olive. From here on all three nymphs shall be referred to as sunken nymphs.
There are some similarities between the sunken nymph and the Killer Bug. They are both tied with wire and are designed to be fished sub-surface. That, however, is where the similarities end. The sunken nymph is designed to imitate a sub-surface nymph rather than a bottom dwelling crustacean. The sunken nymph pattern is generic and not intended to represent one particular species. The inventor of the Pheasant Tail Nymph, observed that swimming nymphs tuck in their legs and appendages and so he dispensed with these when he designed the artificial. It is this simplicity which makes sunken nymphs so deadly – it matches virtually all swimming nymphs found in the world today. This is why it has pride of place in my fishing equipment.
The Netheravon Style of nymph fishing requires quick reactions and a knowledge of what is going on under the water. The take is very subtle and is easily missed if the fly fisher does not anticipate what will happen. If one can see the nymph in the water then things are a little easier but this is rare unless one is lucky enough to fish clear chalk streams and rivers. It is more common to see the fish and even more common to see the leader – both are useful indicators.
Obviously if one can see the nymph and the fish it is simply a case of striking when the nymph disappears inside the mouth of the fish. This requires good eyesight as well as clear water. The fish itself is a useful indicator even if one can't see the nymph. If the fish makes a run and stops then it is likely to have taken a nymph. If it stops in the rough area of where you think your nymph is located then strike. If all that can be seen is the leader, then the trick is to watch for small twitches at the point where the tippet disappears into the water. This can indicate that a fish has taken the nymph.
Regardless of which method of indication is used, one must always bear in mind that the fish will only keep the nymph in its mouth for a fraction of a second before it spits it out. Fish will rarely hook themselves so there is only a very small window of opportunity to strike. Once you have caught the first fish of the day, rub some fish slime on the nymph. This makes it taste more natural and the fish will not be quite so quick to spit it out.