The surface food they are eating is the easiest to establish as it can be seen and usually consists of local insects. Small fish are also a main food source for adult trout and provide them with a large amount of their protein intake, particularly during the ‘back end’. These can be imitated with the use of streamers with colors that represent the main course fish. One feeding habit of trout is to crash into a shoal of fry and pick of the injured ones so using twitched floating representations of injured fry is also a good idea.
Another favorite food for them is insects at the nymph stage of their development, however it is very difficult to determine precisely which ones are being consumed unless you can first catch a fish then examine the contents of its stomach using the marrow spoon. By doing this you can easily determine what insects the trout has recently been eating, and whether it is nymphs, hatching insects or terrestrial insects that have found themselves in the water.
Other protein sources that may be included in a trout’s diet are snails, worms, mice or fish farm food pellets. As a result, there is a large range of flies available but as a general rule, it is best to use a fly that represents a life stage of an insect or fish. There are exceptions to this however, for example during a frog-spawning hatch a tadpole streamer can have great success. At certain points of the year, concentrations of algae cause the ‘daphnia bloom’ and trout eat these microscopic organisms by ‘vacuuming’ them up. Under these conditions, a bright orange streamer is advisable.
When luring a trout, the type of fly used can be a key factor in how successful you are. Floating flies are designed to create surface disturbance to attract the attention of the fish and are made from very buoyant materials such as cork, ethafoam or plastazo. Alternatively, a ‘dry fly’ may be used that is shaped to look like a fully formed insect and is presented to the fish as it rises to the surface of the water.
A long time favorite technique for fly fishing is to use a ‘wet fly’. Here the fly goes under the water and is slowly pulled out using a ‘figure of eight’ manipulation of the line. The figure of eight retrieve is also used when using the ‘Nymph’ fly. Normally, it is weighted and made to go deep, then it is pulled slowly across the bottom of the river.
To fly fish for trout effectively, it is not enough to know how to do it but understanding the diet of the fish in the particular location you are fishing is also vital. By mimicking their food source, you greatly increase your chances of catching the trout and in turn, improve your skills as an angler.