Mostly all fly fishers use the term nymph or nymphing to cover all forms of underwater insect life.
This ranges from true water bred insects that live within the silt and gravel areas of the river, loch or lake until they start to migrate to the surface to hatch into the various flies throughout the seasons.
Also don’t forget the various types of water beetles; shrimps, leeches and snails which spend their whole life in the water.
Due to the various underwater life that are always present, the trout are more often or not pre occupied in feeding beneath the surface and ignore what is happening on the surface.
The trout may be lying in the shallow areas or weed beds feeding on corixa, snails or shrimps or the papue that are trying to reach the surface where they will hatch.
In the event of absence of fish feeding on the surface is a good indication that they are fishing elsewhere. If there is no sign of fish anywhere, the best possible solution is to change from dry/wet flies to nymphs.
During certain times of the day, particularly in the early morning or late evening you may see the trout bulging or swirling as it is possible the fish are taking the nymphs as they are making their way to the surface.
It is essential to determine the depth that the trout are feeding as they could be feeding on the nymphs anywhere between the bottom and the surface.
When fishing with nymphs, they can be fished as a single fly or within a team of various stages of the nymphs life cycle coming up through the water levels. Nymphs can be fished on a floating or sinking
Nymphs can be fished on a floating or sinking line and consideration must be given on how your going to fish them as well.
There is a good choice within the fly fishers armoury when it comes to using nymphs, you can use olives, browns, blacks and greys. If none of these work then you may have to resort to changing the various nymphs until you find the right one for that time of day and month.
If for example there is a large quantity of sedge flies present on the surface of the water and no trout are present taking them, then using a sedge pupa imitation would be your best bet in getting a take. The exact principle works for the other various flies throughout the season: midges; olives and of course the beloved mayfly.
If there are no flies hatching and the water is undisturbed then a good fly to start with would be an imitation of a shrimp, corixa or a snail. It is best to use weighted versions and a longer than normal leader or a sink line to get down to where the trout are feeding.
When fishing nymphs on or near the bottom around weed beds etc and you can see a clear area, it is best to try and get your nymph in the clear area and bring it back slowly along the bottom which can cause the trout to dart out and take your offering.
One of the best nymphs I use in my armoury is a Pheasant Tail nymph with a coloured thorax so that it is more visible to the trout. You can tie this nymph from a size 24 up to a size 8 depending on what your fishing for.