330 REPOKT OF COMMISSIONER OF FISH AND FISHERIES. 



ARTIFICIAL PROPAGATION. 



Artificial propagation in the fish-culturist's sense, the raising of 

 oyster fry from artificially fertilized eggs, has, at the present time, no 

 place in practical oyster-culture. It may perhaps sometime demon- 

 strate its applicability to a system of spat production in small closed 

 ponds, but it can have absolutely no use in the present methods of 

 oyster-growing. It is futile to expect any results from deposits of the 

 swimming fry upon beds planted in the open waters of the bays and 

 sounds where the conditions are usually such as would bring about a 

 wide distribution. Fry so deposited would be, no doubt, largely carried 

 to other beds, and be lost to the man who planted them, or else would 

 fall upon unsuitable bottom. Their fate after being deposited in the 

 water is so uncertain that, in our present state of knowledge, it 

 would be a w^aste of eflbrt for either Government hatcheries or private 

 individuals to attempt to increase the oyster by such means. 



If, however, there can be devised some successful method of closed- 

 pond production, then artificial propagation may find a field of useful- 

 ness. Dr. Eyder suggested that the available amount of fry in his 

 method of spat-culture might be increased by adding embryonized 

 water to the inlet to the sluice at the beginning of flood tide, the 

 embryos being carried up through the cultch upon the flood and back 

 again upon the ebb, thus giving a double chance for fixation. There 

 is no doubt but that the proportion of eggs successfully fertilized can 

 be increased by the artificial mixture of the ova and spermatozoa 

 according to methods which science has demonstrated. 



Another experiment by the same investigator showed that spat could 

 be raised in a practically closed pond from artificially fertilized eggs. 

 The experiment was briefly as follows: The pond was excavated in the 

 salt marsh on the sliore of Chincoteague Bay. It was about 20 feet 

 square and 3^ feet deep, and communicated with the bay by a canal 10 

 feet long, 2 feet wide, and the same depth as the j^oud. The mouth of 

 the canal was closed with a filter composed of boards perforated with 

 auger-holes and lined inside with gunny-cloth or bagging. The boards 

 constituted two diaphragms, an inner and outer, the interval of 2 inches 

 between being filled with clean sharp sand. Through this the tide 

 ebbed and flowed, giving a rise and fall of from I to 6 inches during 

 the interval between successive tides. 



This filter, like most structures of its class, showed a tendency to 

 clog after it had been in use for some time, and as, from its shape, it 

 was difficult to cleanse, Dr. Eyder devised the following arrangement, 

 which is accessible at all times and in which the sand may be renewed 

 at will: 



My improved permeable diaphragm is placed liorizontally within an oblong 

 trunk or box, A, fig. 1^ of plate IV. The box is made of inch planks, to which strong 

 horizontal sidepiecea, a, ligs. 2 and 3; are secured, and to which are fastened the 



