It may seem somewhat superfluous to say that fish cannot live in any water unless that water contains the food supply necessary for them to thrive upon, and yet this is the point most often overlooked in stocking waters with fish. Small attempts at stocking with creatures suitable for food, particularly after the fish have been already introduced, are not at all likely to succeed. Such an important matter when treated as a small afterthought is almost sure to end in failure of the whole business of stocking.

But a small amount of thought will convince any one that in order that there may be a sufficient amount of animal life in a water, there must be an adequate vegetable life, for weeds are almost always necessary to the well-being of the creatures which serve as food for fishes.

In the case of a pond it is generally fairly easy to introduce a good stock of suitable weeds. The best method is to let the pond down as low as possible, and then to plant some weeds round the margin; the water is then allowed to gradually fill up the pond, and as it rises weeds are planted round the rising margin of the water. In ponds which cannot be emptied at all, or not sufficiently to carry out this plan, weeds may be planted in an easy but not quite so effectual a manner. They may be planted in shallow baskets containing some mud from the bottom of the pond, and then lowered in suitable places from a boat, or bundles of the weed may be tied to stones and dropped into the water in a similar manner.

These latter methods are, of course, not so good as actually planting the weeds round the advancing margin of the water, for success depends to a certain extent upon chance. Some of the weeds thus planted are, however, sure to take root and grow. Plants of different kinds, of course, are necessary at different depths and on different kinds of bottoms, and good kinds are necessary at the margin of the water as well. I give a list of some suitable plants of each kind at the end of this chapter.

Similar methods are used in planting weeds in rivers and streams to those used in ponds. If the weeds are planted in baskets, the baskets must, of course, be weighted when put in a position where the current can act upon them.

Besides vegetation in the water, vegetation on the bank is of considerable importance. I shall deal with this at a later period more fully, as trees and bushes, besides harbouring many insects which serve as food for fish, have also considerable importance in giving cover to the fish and to the fisherman who is pursuing them.

I think that in the case of a bare water, a year at least should be devoted to developing a good supply of vegetation. This will generally produce a considerable amount of animal life, without any artificial help, but judicious help will be sure to accelerate matters to a considerable extent. I would, however, advise the amateur not to attempt to introduce a quantity of creatures into his water, until the vegetable life therein is well established. For instance, though fresh-water snails are desirable in every trout water, if introduced in large numbers into a water in which the vegetation is small and not well established, they will eat down the weeds too much and then die off from disease caused by want of sufficient nourishment.Having established the vegetable life well in a water, and developed it to a considerable extent, the amateur may begin to examine his water, and find out how much animal life exists there, and to stock with creatures suitable for food, according to what he finds in the water.

Fresh-water snails are always desirable. In streams, or in ponds with streams running into them, the fresh-water shrimps (Gammarus pulex) should always be tried. It does not do in some waters, but where it does thrive it increases very rapidly, and forms about the best article of food that can be given to trout. CorixÆ, which thrive in ponds and sluggish waters, should always be introduced. They increase rapidly, and are taken by most fish, particularly by trout. The amateur should be careful when he introduces these creatures to make sure that he is putting in the right creature. The water-boatman (Nautonecta glauca) is a member of the same family, but is no use as food for the fish. He swims on his back, is longer and narrower than are CorixÆ, which do not swim on their backs, are smaller, broader, and live much more under water than the water-boatman. It is generally advisable to avoid water-beetles, as most of them are more likely to do harm than good, such a number of our water-beetles being carnivorous. They will probably not harm adult fish, but they will destroy ova and fry. I have known a Dytiscus marginalis kill a trout of nearly a quarter of a pound in weight.

In order to make sure of not introducing carnivorous water-beetles into a water, I think it best as a rule not to introduce beetles at all. CorixÆ are, however, so like beetles, that many people call them beetles, and therefore I will give a few points which will make them easily distinguishable from each other. In beetles, the wing-cases (elytra) meet exactly in the middle line, in CorixÆ and other water-bugs, the anterior wings, which resemble the elytra of beetles, overlap, which causes the line on the back to curve away to one side at the lower end. In beetles the wings which lie under the wing-cases are folded up on themselves, and when spread out are much larger than the wing-cases. The wings are transparent and very delicate. In CorixÆ the posterior wings, which lie under the hard and horny anterior wings, are a little shorter than the anterior wings; they are not folded up on themselves and are not so delicate and transparent as the wings of the beetle.Such small creatures as Daphnia pulex, Cyclops quadricornis and Rotifera should be introduced into ponds.

Snails (Gasteropoda) may be roughly divided into three classes, according to the shape of their shells: (1) Flat-shaped coils (type Planorbis corneus); (2) Oblong-shaped, somewhat like a trumpet (type LimnÆa stagnalis); and (3) Ear-shaped (type LimnÆa auricularia). LimnÆa auricularia is particularly suitable for deep waters, and L. pereger, whose shell is of type 2, is a most valuable addition to the food supply in any fish pond. It is one of the commonest of our fresh-water snails.

Mussels (Conchifera) are another valuable article of food. There are a great many different kinds, and the larger ones should, as a rule, be avoided. SphÆriidÆ and Pisidia are probably the best.

In many cases it is advisable to attempt the introduction of some flies which are not present. There are several cases in which the May-fly has been successfully introduced, and also the Grannom. Small EphemeridÆ seem to me preferable to any other flies.

With regard to suitable plants for comparatively deep water in ponds or lakes, lakewort and stonewort grow on the bottom, and do not, as a rule, attain any considerable height. White and yellow water-lilies also grow in fairly deep water; the water-lobelia is also an excellent plant for ponds.

In streams some of the best plants are water-crowfoot, water-starwort, and the great water moss. Anacharis should not be introduced into any water, either pond or stream, unless it can be kept down easily. It will otherwise become an unmitigated nuisance.

Marginal plants are a very important consideration, and plenty of them should be grown. Water-celery and water-cress are perhaps the best food-producing marginal plants that can be grown. Bullrushes and brooklime are also good, but the bullrushes must be planted judiciously.