The limits of this article do not permit the discussion of work in connection with the fisheries, or of the scientific investigations which form the bed for the whole current of its activity.
The principal activity of the Commission has properly been directed to the wholesale replenishment of our depleted waters, as is shown by the fact that from seventy-five to eighty-five per cent. of the appropriations have been directed into this channel.
For fifteen or twenty years prior to the establishment of the Commission, popular interest in the fisheries, and a desire for their maintenance had been on the increase, the state of public opinion being doubtless under stimulation from the action of the French government in fostering the still infant art of fish culture.
The publications and experiments of Garlick, Fry, Atwood, Lyman, Green, Stone, Ainsworth, Roosevelt, Atkins, Stady, and others, awakened everywhere a sense of the fact that our rivers and streams were being rapidly cleared out, and the feeling that a similar state of affairs was probably existing in the adjoining ocean. Measures were set on foot for restoration and protection as early as 1605, when Massachusetts appointed the first commission, and prior to 1870 this example was followed by several other states. Nearly all the states and territories now have similar organizations. The United States has distanced all its competitors, as was evinced by the manner in which the prizes were distributed at the recent fishery exhibitions in Berlin and London.
The fertilization of the fish egg is the simplest of processes, consisting, as every one knows, in simply pressing the ripe ova from the female fish into a shallow receptacle, and then squeezing out the milt of the male upon them. Formerly a great deal of water was placed in the pan, now the “dry method,” with only a little water, discovered by the Russian Vrasski, in 1854, is preferred. The eggs having been fertilized, the most difficult part of the task remains, namely, the care of the eggs until they are hatched, and the care of the young fry until they are able to care for themselves.
The apparatus employed is various in principle, to correspond to the physical peculiarities of the eggs. Fish culturists divide eggs into four classes, viz.: (1) heavy eggs, non-adhesive, whose specific gravity is so great that they will not float, such as the eggs of the salmon and trout; (2) heavy adhesive eggs, such as those of the herring, smelt and perch; (3) semi-buoyant eggs, like those of the shad and whitefish (Coregonus), and (4) buoyant eggs, like those of the cod and mackerel.
Heavy, non-adhesive eggs are placed in thin layers, either upon gravel, grilles of glass, or sheets of wire cloth, in receptacles through which a current of water is constantly passing. There are numerous forms of apparatus for eggs of this class, but the most effective are those in which a number of trays of wire cloth, just deep enough to carry single layers of eggs, are placed one upon the other in a box or jar, into which the water enters from below, passing out at the top.
Heavy, adhesive eggs, are received upon bunches of twigs, or frames of glass plates, to which they adhere, and which are placed in receptacles through which water is passing.
Semi-buoyant eggs, or those whose specific gravity is but slightly greater than that of the water, require altogether other treatment. They are necessarily placed together in large numbers, and to prevent their settling upon the bottom of the receptacle, it is necessary to introduce a gentle current from below. For many years these eggs could be hatched only in floating receptacles placed in a river, with wire cloth bottoms, placed at an angle, the motion of which was utilized to keep the eggs in suspension. Later, an arrangement of plunging buckets was invented, cylindrical receptacles with tops and bottoms of wire cloth, which were worked up and down at the surface of the water by machinery. The eggs in the cylinders were suspended in rows from beams which were worked up and down at the surface of the water by machinery. The eggs in the cylinders were thus kept constantly in motion. Finally, the device now most in favor was perfected; this is a receptacle, conical, or at least with a constricted termination, placed with its apex downward, through which passes from below a strong current, keeping the eggs constantly suspended and in motion. This form of apparatus, of which the McDonald and Clark hatching jars are the most perfect developments, may be worked in connection with any common hydrant.[A]
Floating eggs have been hatched only by means of rude contrivances for sustaining a lateral circular eddy, or swirl of water in the receptacle.