This section is from the book "Fly Fishing", by Sir Edward Grey. Also available from Amazon: Fly Fishing.
To hook a trout which has risen to a floating fly, it is necessary to strike, for the simple reason that a fish cannot be hooked on a slack line, and that it is impossible to float a fly naturally without allowing the line a certain degree of slackness. The line may be straight upon the water, but a floating fly cannot be kept in touch with the point of the rod in the same way as a wet fly, which is being jerked through the water or being swept round at the end of a line kept extended by the stream. The rise of a trout is sometimes described as though the fish took the fly with a dash from below, and then turned sharply down and hooked himself by his own weight. This may be the case with a wet fly moving under water, but it is as a rule not the way in which a large chalk stream trout feeds. He lies close to the surface of the water, and takes by preference the flies which pass exactly over him, taking them with the smallest possible effort and change of position; often he does little more than just put the end of his mouth to the surface and withdraw it, taking the fly with the mere tip of his lips, and rejecting it instantly if it is not what he expects. It seems to me better therefore (though authorities differ about this) to strike directly the fly is seen to be taken. There must in every case be a perceptible interval required to overcome the slackness of the line before the strike takes effect, and where, as often happens, the line owing to the manner of the cast or the action of the stream is not perfectly straight upon or in the water at the time, this interval is sometimes too long rather than too short. Large trout, which have probably had some previous education, are apt to feed very carefully and to take the fly so delicately, that the angler often has only half a chance of hooking them at all, and that only at the exact moment when the lips close upon the fly. Any angler may notice how many of his large trout are hooked in the very edge of the mouth. I have sometimes, when I could see the fish in the water, intentionally abstained from striking in order to see what happened, and the result has been that, though very small and innocent trout have sometimes taken the fly with a confident gulp, and have had apparently a little difficulty in expelling it under water afterwards, the larger trout have rejected it in an instant. Where, however, the movement of a trout can be watched in the water, great care is needed to avoid striking too soon; for if the approach and opening of his mouth—the sure signs that he is going to take the fly—are mistaken for the fact of his actually having done so, the trout will certainly be missed and probably be scared.
The art in striking is to use the greatest amount of quickness and decision that can be combined with gentleness; personally I prefer to strike with the hand upon the line, rather than to be dependent upon the nice adjustment of resistance in the reel; and whatever may have been the case in early and more excitable days, I do not find much difficulty now in preventing myself from striking too hard. But nothing is more annoying than to lose a good trout by striking too hard; the fish then often gives a heavy plunge in surprise and alarm, which increases the idea of its size, and the angler overwhelms himself in consequence with bitter self-reproach. When the gut does break it is generally at the knot which holds the fly, and to guard against this misfortune there are two precautions which no angler can impress upon himself too much. The first is, to soak the end of gut well, not merely at the beginning of the day, but also on every occasion before tying on a new fly; without doing this he cannot be sure of tying a sound knot. The second is, to examine the gut at the head of the fly carefully from time to time. Sooner or later the constant flicking will weaken fine gut, even when the smallest flies are used. Sometimes the gut at the head of the fly becomes untrustworthy in five minutes; sometimes it lasts a long time unimpaired. The length of time the gut lasts depends upon the angler's manner of casting and drying his fly, which in its turn will vary with the position of different fish and the angle of the wind. In old days before the use of eyed hooks this weakening of the gut at the head of the fly was a real nuisance; on some days fly after fly had to be thrown away (if it was not actually whipped off) after a little use, but now it is an easy matter to tie the fly on again. It should, however, be remembered that a new fly is more perfect in shape and more attractive than one which has had much whipping to and fro, and, where trout are large and shy, it is better to put on a new fly pretty frequently, and to do so always after landing a fish.
The moment after hooking any trout of two pounds or upwards is generallyone of great anxiety. Sometimes the fish pulls steadily from the first, but one in really fine condition generally goes off with a rush, as if it realised in a flash the full horror of the mistake it had made. Fine gut cannot stop such a trout at first, and all the angler can do is to handicap it by putting on as much strain as he dare. This is the great crisis: the rise, the strike, and the rush succeed each other in a moment, and the angler's emotions are an exquisite blend of joy and fear. If the trout is clearly making for a bed of weeds it is best to let it go in rather than to risk a break: if it is lightly hooked it will free itself from the fly in the weeds, but it may do this in any case. On the other hand, if the trout is firmly hooked, it is surprising how often the angler is able to extricate his fish by lowering the point of his rod, keeping the line tight and working it gently with his hand. Time after time I have known fish, apparently buried in weeds, be perfectly immovable by the strain of the rod and give no sign of feeling it, and yet become restless and yield to the direct play of the hand. It is, of course, essential that the strain should be applied from below the weeds. It is, in my opinion, an error to suppose that the idea of a trout is to roll itself up in weeds and thus to offer resistance: its first object is probably shelter out of sight, but a trout's method of resisting in weeds is, I am convinced, to lay hold of them with its mouth. For years I had noticed that there were generally pieces of weed actually in the mouth of fish that were landed after being hung up in weeds, but it seemed to me unlikely that they really seized the weed with their mouths deliberately. One day, however, I happened to be playing a trout on a clear shallow, where there were no large patches of weed, and where every movement could be seen : the fish came near a small piece of weed and stuck there, and the strain on the rod became that of a dead weight. The thing looked absurd, for the weed was much too small to conceal the fish, and only the head was in contact with it. There was nothing but this ridiculous little patch of weed and the trout—a fish of not much over a pound—and yet I could not move it! When the fish was landed, there as usual was some weed inside the mouth. It will of course occur to any one as a possible explanation (and so it did to me), that the line may have got round the little patch of weed, and so caused the feeling of pulling at a dead weight; but it appeared to me at the time that this was not so, and subsequent experiences of the same kind in shallow water, where I have been wading close to the fish, and have been able to examine the situation at leisure in every detail, have convinced me that trout do attempt to resist the strain of the tackle in the way described.1
 
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