Young salmon, young salmon trout, California mountain trout, and above all young California salmon are larger, have stronger appetites, and will accept coarser food. For them, although at first the liver should be made as fine as for trout, when they are a few weeks old it will be hardly necessary to dilute it at all, and in the course of a few months they will not only take the larger pieces, often tearing them apart, but will scorn the finer portion. At one time sour milk was almost exclusively used for feeding young fish, but it has been given up. Other foods have been tried, but with no better success. The fish will not thrive on any of them as well as they do on liver, and do not thrive on that as well as if it were a natural food. Near the salt water, where soft clams can be obtained, they are used in place of liver.
As they grow older, other things may be substituted or may be added to it as a change. They are fond of the roe of other fish, of the spawn of the horse-foot or king-crab; of fish itself, and when they are large enough to eat minnows, no better food can be given them. Liver is too expensive when it has to be used alone for grown fish, and beef lights are usually added to it or used in place of it in a measure. It is miserable food, however, much of it passing through the stomachs of the trout and salmon wholly undigested and collecting in the bottom of the ponds. It injures the digestive organs and must be deleterious to the health of the fish. Its only recommendation is that it is cheap. Maggots are bred on spoilt meat, hung over the ponds, and as they fall off and drop into the water are readily devoured, and make excellent food. Or a piece of spoilt meat may be placed in a deep bottle like a preserving bottle, and the flies that will collect in immense numbers during summer may be caught and emptied into the water. This trap will take many times its bulk of flies being kept set all the time and emptied when any one is passing it. Flies are probably the best food that can be given to trout.
Shad eggs differ essentially from trout eggs and require wholly different manipulation. They are much smaller and lighter. If a trout or salmon egg is dropped into water it sinks at once to the bottom, but a shad egg will almost float, and has but little more specific gravity that the water itself. Shad eggs are less than half the size of trout eggs, and require as their best condition for hatching a temperature of from sixty-five to seventy-five degrees. They will hatch at a lower temperature, but in such cases mature slowly, while eighty degrees of heat is as much as they can endure. When experiments were first made in their artificial propagation, they were placed in ordinary trout troughs, and much trouble was found in their management. If a current of water was turned on to the same extent as with trout, they all washed over the end of the troughs, while if the supply was diminished so that they retained their places, they died of suffocation. It was only after many different devices had been tried that the proper invention was discovered—a simple box with the bottom knocked out and replaced by a wire gauze netting. This box is suspended by floats of wood nailed on the sides, so that the bottom is presented at an angle to the current, the degree of inclination being determined by the velocity of the current. The water striking against the screen enters the minute interstices, and lifting the eggs, keeps them in gentle motion like the bubbles of air in a pot of moderately boiling water. All that is necessary is to attach these boxes one behind the other in a long row, anchor them in the river, and fill them with impregnated spawn, and the work is done. The continuous motion of the water passing around each egg and holding it suspended, aerates it perfectly and makes its hatching a certainty. Hardly one per cent. of healthy eggs fail to hatch, and while the process is going on hardly any care or attention is required. Fish and eels cannot enter the boxes to prey, nor can the eggs be driven out by the water, and lost.
In the artificial manipulation of shad the parents are taken in seines from their spawning beds. The haul is made at night, at which time only can ripe fish be found in any considerable number. The captured fish are thrown indiscriminately into a boat and are stripped at once as they die quickly. They are afterwards sold in the markets. The eggs, which are caught in a pan with a little water in it, after being allowed to stand for a few minutes until impregnation is complete, which is signified by their swelling in size and reducing the temperature of the water some ten degrees, are poured into the hatching boxes and left to themselves. Nothing more is required. In twenty-four hours the black eyes of the young fry will be visible through the shell, and in from three to ten days they will be hatched.
Black bass is one of the most prolific varieties of our fresh-water fish. Their natural increase is so great and their growth so rapid, that it has never been an object to fish culturists to attempt their artificial propagation. When the spawning season draws near, they select, guided by natural instinct, with great care for the purpose of propagation, certain portions of the river having a pebbly or gravelly bottom. From these they remove carefully all sediment, weeds, and sticks. This work completed, leaves a clear bright space in the bottom of the river, circular in form, and having a diameter of about three feet. These beds are readily distinguished by the casual observer from the ordinary bottom of the river by their brightness, the gravel having the appearance of being washed or scoured. When the parent fish are ready to spawn, the female goes upon this prepared bed and deposits her spawn in a glutinous band or ribbon, running in various directions across the bed. She is followed by the male who impregnates the eggs by the expression of his milt.
Their care of the young (the exercise of which is peculiar to the bass, sunfish, and catfish), taken in connection with the fact that a large pair of bass will deposit twenty thousand eggs, will give some idea of their fertility. Possibly the fish are capable of reproduction when two years old, having at that time attained the extraordinary length of eight or nine inches, but this is mere conjecture, based more particularly upon our knowledge of the size and weight of the fish at that age. They frequently attain the weight of five and six pounds; in rare instances seven and eight. They are unsurpassed in flavor by any of the perch family.
The black bass loves bright, pure, lively water, not as cold as the trout streams of our spring-producing hills and mountains, but free from foul matters held suspended in it, and with motion either of current or from the winds. It deposits its eggs on rocky or pebbly ledges. The parents guard and protect their nests till the young are hatched, and even watch over the latter till they can take care of themselves. The fish generally selected for transfer are from one to three years old, measuring from three to twelve inches in length. Fish of this size are not only more numerous, but they bear transportation better, and are more readily acclimated than when larger. They are moved with a great deal of difficulty in hot weather, especially when the journey requires more than twelve or fifteen hours; but with care and skill no serious loss need take place.
The implements of the fish-culturist are few and simple. A few feathers may be kept on hand to use in spreading the eggs when placing them in the troughs, in collecting them for packing, and moving them in the search after dead eggs. Nippers made of wire or some elastic wood, like red cedar, bent or cut into the shape of the letter U, elongated to about six inches, and with loops of wire at the ends about the eighth of an inch wide, will hold an egg without trouble. A small homœopathic phial is used to examine the eggs. The manner of its use is, to fill it with water, put in the eggs to be examined, cork it, hold it up before the window in a horizontal position, and with your microscope look up through the side of the phial. This brings the egg which lies at the bottom of the glass within the focus of the microscope, and the water does not distort its shape. The microscope need not be very strong; one magnifying eight or ten diameters is amply sufficient. A small net will be of use in removing the young fish and any refuse in the water from the troughs; it should be about six inches in diameter, in the shape of the letter D, with the handle on the middle of the bend. It is very easily made by bending a wire in the desired shape, and twisting the two ends together for a handle. Thin gauze of some kind, like bobinet, should be spread over the wire so tightly that the middle of the net shall hang only a half inch below the level. An iron spoon, well tinned or silvered, is used to remove the eggs. Some six-quart tin milk-pans will be necessary, for a variety of purposes. Eggs may be counted most easily by measuring them. For this purpose take any small glass, such as a very small tumbler, for instance, count out five hundred or a thousand eggs, and with a file make a mark upon the glass as high as they reach, and the measure is always ready to your hand.
A watering pot with a fine rose spout is used to wash sediment from the eggs on the sieves, and a broom of twigs is used to brush the screens of wire.
One of the most curious and interesting results of fish-culture has been the production of hybrids, some of which were reproductive and have thus created new species. Strange as it may seem, these experiments have rarely been wholly abortive; no matter how dissimilar the families, the eggs have been impregnated often to a large percentage, and have hatched. The following varieties have been crossed: