Trout and grayling are by no means the only species of fish you catch by fly-fishing. Dace, chub and rudd are great risers to a fly. Chub especially can be interesting to catch on a dry fly during hot weather when they can be seen in shoals just below the surface. Rudd are predominantly surface feeders and fly-fishing for them on a summer evening can produce huge catches. Dace take a dry fly very fast and can be fun to learn on. Perch are regularly caught by anglers fishing with lures on the big reservoirs. Often these perch are of a larger than average size. Pike too will grab a lure as it passes their nose ends. The only problem with hooking pike on fly tackle is that they are likely to bite through the nylon leader.
Fly-fishing can become very absorbing and, once you learn how to do it, a very productive method.
Angling is a very complex subject and to achieve consistent success the angler must learn more than tackle-control and the basic habits of fish. He has to learn about the environment in which fish live and how changes in this environment affect fish behaviour.
A river is not just a mass of water draining the land and rushing out to sea, but a very complicated ecological system. Many forms of wildlife are dependent on a river both under the water and along its banks. There are many different types of river from slow, meandering, lowland rivers to torrential mountain streams, each providing a habitat for the different species of fish within them.