GENERAL CONSIDERATIONS. The maintenance of artificial ponds for the rearing of fresh-water fishes for food or ornamental purposes is a very ancient practice, and is carried on by nearly every eivilized,nation. In China fish culture has been extensively practiced from ancient times. In Europe. and particularly in Germany and Sweden, pond culture is of considerable impor tance. In recent years, however, fish culture has become almost synonymous with the harvesting of eggs, their artificial fecundation, and the rearing of the young up to varying stages in hatcheries established for that purpose. This seems to have been an ancient custom in China, where the Europeans probably got their first ideas of modern pisciculture. Both in Europe and America the industry has become of such im portance as to be more or less completely sup ported by Government funds. In Europe the hatcheries, over four hundred in number, are .largely private enterprises. but such are as yet comparatively rare in the United States and Canada. The United States far surpasses all other countries in the extent of this work under Government patronage. The Federal Government supports twenty-eight hatcheries at various fa vorable places, and one steamer, the Fishhawk, a sort of floating hatchery, exclusively used in the actual culture of fishes or in the investigation of problems pertaining thereto. The number of fish handled in 1899, either as eggs. fry, finger lings, yearlings, or adults, aggregated 1,056.371, 898. Of this number 9S6,000,000 were fry and fingerlings, and 5,000,000 yearlings and adults. Besides these many of the States support hatch eries for the particular fishes of importance in their territories. (See below.) The purpose of thegovernmental hatcheriZs is either to stock new waters with desirable species or to maintain by planting the supply in waters already tenanted.
In most species it is impracticable to carry culture much beyond the stage of hatching, or 'fry,' as the hatchings are called. This is true of
all the strictly marine forms such as the cod and flat fishes. In many of the fresh-water species, such as the various salmons and sun fishes, they are often nourished and protected in suitable ponds until they have become three or four inches long--`fingerlings,' as they are then called—before planting. They may even be car ried for another year and planted as yearlings.
It is now established that waters thus stocked or replenished have not only been able to main tain their supply of fishes, but have greatly increased' it. Pacific waters have been success fully stocked with Atlantic species, and almost exhausted streams in various parts of the United States have been successfully restored. In some species the eggs are not handled, but the spawn ing fishes are provided with favorable ponds for spawning purposes. where their eggs are pro tected from enemies, given suitable temperature, etc. This is the case with members of the Cen trarchidte, such as the black bass, which build a nest and guard the eggs during incubation. The young when hatched are either taken from the ponds and fed in suitable troughs until better able to shift tor themselves, or are supplied with food in the ponds themselves. In most species, however, the eggs -are artificially expelled from the body into suitable receptacles, in which they are fertilized by the addition of milt similarly obtained from the males. After a few moments the eggs are transferred to running water, where they are kept and taken care of until the embryos emerge. The exact method employed in fertiliza tion, but especially the subsequent handling of the eggs during incubation, varies considerably with the character of the egg.