It is thought that the last clause of this passage refers, not to the actual capture of the Fish, but to the mode in which they were kept in the tanks, each being secured by a ring or hook and line, so that it might be taken when wanted.
On referring to the New Testament, we find that the fisher Apostles used both the hook and the net. See Matt. xvii. 27: "Go thou to the sea, and cast an hook, and take up the fish that first cometh up." Now this passage explains one or two points.
In the first place, it is one among others which shows that, although the Apostles gave up all to follow Christ, they did not throw away their means of livelihood, as some seem to fancy, nor exist ever afterwards on the earnings of others. On the contrary, they retained their fisher equipment, whether boats, nets, or hooks; and here we find St. Peter, after the way of fishermen, carrying about with him the more portable implements of his craft.
Next, the phrase "casting" the hook into the sea is exactly expressive of the mode in which angling is conducted in the sea and large pieces of water, such as the Lake of Galilee. The fisherman does not require a rod, but takes his line, which has a weight just above the hook, coils it on his left arm in lasso fashion, baits the hook, and then, with a peculiar swing, throws it into the water as far as it will reach. The hook is allowed to sink for a short time, and is then drawn towards the shore in a series of jerks, in order to attract the Fish, so that, although the fisherman does not employ a rod, he manages his line very much as does an angler of our own day when "spinning" for pike or trout.
Sometimes the fisherman has a number of lines to manage, and in this case he acts in a slightly different manner. After throwing out the loaded hook, as above mentioned, he takes a short stick, notched at one end, and pointed at the other, thrusts the sharp end into the ground at the margin of the water, and hitches the line on the notch.
He then proceeds to do the same with all his lines in succession, and when he has flung the last hook into the water, he sits down on a heap of leaves and grass which he has gathered together, and watches the lines to see if either of them is moved in the peculiar jerking manner which is characteristic of a "bite." After a while, he hauls them in successively, removes the Fish that may have been caught, and throws the lines into the water afresh.
We now come to the practice of catching Fish by the net, a custom to which the various Scriptural writers frequently refer, sometimes in course of historical narrative, and sometimes by way of allegory or metaphor. The reader will remember that the net was also used on land for the purpose of catching wild animals, and that many of the allusions to the net which occur in the Old Testament refer to the land and not to the water.
The commonest kind of net, which was used in the olden times as it is now, was the casting-net. This kind of net is circular, and is loaded all round its edge with weights, and suspended by the middle to a cord. When the fisherman throws this net, he gathers it up in folds in his arms, and, with a peculiar swing of the arms, only to be learned by long practice, flings it so that it spreads out and falls in its circular form upon the surface of the water. It rapidly sinks to the bottom, the loaded circumference causing it to assume a cup-like form, enclosing within its meshes all the Fish that happen to be under it as it falls. When it has reached the bottom, the fisherman cautiously hauls in the rope, so that the loaded edges gradually approach each other, and by their own weight cling together and prevent the Fish from escaping as the net is slowly drawn ashore.