This section is from the book "The Goldfish And Its Systematic Culture With A View To Profit", by Hugo Mulertt. Also available from Amazon: The goldfish and its systematic culture.
Among fish culturists it is the universal custom to divide fishes into two classes according to the season in which they spawn; we thus have summer spawning and winter spawning fish. They are further more distinguished as they differ in the mode of depositing the eggs, as some are laid on or in receptacles usually called "nests," especially prepared by the fish for that purpose, and others again are dropped loosely into the water without any precautions having been taken for their protection. In the latter case they again differ in being either "adhesive" or "non-adhesive," in the one instance adhering to anything they may happen to touch and remaining until hatched, in the other sinking to the bottom or floating about at random on the surface.
The goldfish belongs to the summer spawning class, builds no nest and its eggs are adhesive in the full sense of the word. In those fish depositing non-adhesive eggs, the extrusion of them by hand, and their artificial impregnation is profitable, but with the carp-like fishes, a higher percentage of young is obtained when the spawning is allowed to proceed in its natural manner. Besides, their eggs not being mature all at the same time, would make the operation of extrusion an oft-to-be repeated affair, and which, furthermore, would greatly endanger the life of the fish and require much time and attention.
Goldfish raising is therefore confined to: -
I. Guiding Nature with regard to the "survival of the fittest, " and with it of course the pure strain.
II. Assisting Nature by securing suitable spawning resorts. III. Regulating the spawning season, and
IV. Protecting their spawn and young.
As soon as the spring weather sets in with sufficient sunshine to affect the temperature of the water, the fish in their winter quarters rise near the surface and become lively again. This is the time to get the spawning beds ready for action. Whatever month or date that may be, is determined by the respective locality of the ponds, viz., their situation in a northern or southern climate, and there, whether they are exposed or protected. The beds are then filled with water to the proper level, and all details concerning the pond are attended to, so that it will be in complete running order. When all is ready, the fish from which it is intended to breed are selected, and right here reside the fundamental conditions upon which depend the production of a good and saleable crop of fish. The fish used to breed from should be healthy in every respect, of good shape and color, and of gentle, fully domesticated habits. All these qualities will be inherited by their young. In regard to the color of the fish, it is of great importance to know at what age this was acquired, as such fish that colored at an age of six to eight weeks transmit the same tendency to their young on an average of 98%. In contrast with this, those fish whose coloring was delayed until the second year, when bred, produce but 5% of young that will color in the first year, while the remainder do not assume their red, yellow, or white coloring until the second year, a great many never changing, always remaining "silver" fish.
The coloring attained by the fish generally remains so, though there are instances in which the red markings may become milky white, and what was previously white changes to red, or black spots may appear, or if present, be lost. This may occur either wholly or in part. A satisfactory reason for this phenomenon can not be given.
The selection of faultless beauties for breeding purposes, however, is not absolutely necessary, such specimens are best kept for exposition purposes. Any fish whose fins may have become injured in any way, by accident or otherwise, but have grown again in some crooked or objectionable shape, are nevertheless perfectly fit for the spawning bed, if they are otherwise in perfect condition, though for ornamental purpose they would be of little account.
It may be remarked in this connection, and with propriety, that certain peculiarities in the shape of foreign fish, i. e., those newly introduced, are in the course of time, lost, when imported into the United States, the change of climate, locality, food, etc., producing gradual changes in their typical forms, assuming or acquiring, so to speak, an American type. In view of this, the culturist should never neglect to infuse new blood into his stock whenever a favorable opportunity offers, for by so doing he can keep it up as near to the original standard as it is possible to do under the change of circumstances.
At the breeding season the sexual differences are plainly revealed to the practiced eye of the patient observer - not before. Upon close inspection the bony plates that cover the gills, the gill-covers, or opercles, will be found covered with small white prominences, usually denominated tubercles. Those fish bearing this distinguishing ?nark are male fish. These tubercles appear on the fish when it is in condition for reproduction, and disappear when that function ceases to be in an active state. This period may be of longer or shorter duration in different individuals, and it will also be seen that the number of the tubercles will vary in the different specimens upon which they are observed. (See illustration.) The usual method of distinguishing the male from the female by noting the presence of a short dorsal fin is not reliable; in fact, it is not only misleading, but false, as such short, or more properly speaking, "deformed" dorsal fin, is found just as frequently upon female fishes. The tubercles are sharp, very similar to the projections upon a rasp, and seem to have for their function the assisting of the female to pass its eggs through the canal. This theory is apparently substantiated by the fact that the male uses them in such a manner by pressing against the belly of the female that one is irresistibly led to the conclusion that they can exist for no other purpose.
The females to be selected must show an expanded belly, which evidences the maturity of the eggs, as it has been stated before, that when arrived at that period, they increase in size, and it is by this appearance only that the culturist can decide that the time for the female to spawn has arrived.
It is worse than useless to place in the spawning bed fish that are not in perfect condition to perform the functions, as some goldfish are sterile, and will only disturb the arrangements that have been so carefully made for that purpose. Whether these particular fish will remain sterile for a season or for as long as they live can not be decided. As a rule, it is best to select three females and four males when of good size, or six females and four males, when the former are small yearlings, for each spawning bed. It is also important to match the sizes of the fish; should this not be possible, in case the females are larger than the males, two or three males may be required to mate with the females. The best age for spawners is that between two and four years.
Head of Male Goldfish.
The selection having been made, all those fish not wanted for present use are returned to the winter pond.