76 DEPARTMENT OF THE NAVAL SERVICE 



8 GEORGE V, A. 1918 



it may be mentioned that tlie gar, including at least the two species L. platostomus and 

 L. osseus, has been found to be practically the only host for one of the most desirable 

 of shells, the Yellow sand-shell (Lampsilis anodontoides). 



In actual artificial infection of fish the operation is essentially as follows : The 

 gravid mussels and their suitable fish hosts are placed in a vat or tub containing a 

 requisite amount of water. The mussel is now opened, the marsupial pouch split open 

 along its ventral border and the glochidia are squeezed out into one of the valves 

 of the mussel, which valve also serves as a small water container. The glochidia are 

 then poured into the tuib and the water agitated, more or less, so that they will be 

 kept in suspension. From time to time individual fish are caught and gills examined 

 to determine the extent of infection. The optimum amount of infection varies for 

 different sizes and species of fish and also for the condition the fish are in. It is 

 generally accomplished within the limit of 5 to 20 minutes. Over-infection must be 

 guarded against. 



Naturally, there cannot be any definite rule as to the number of glochidia to be 

 used with any number of fish, the person in charge must be guided by his experience. 



When sufficiently infected, the fish are removed to the river or pond. If develop- 

 ment in the gills is to be watched, they may be transferred to crates anchored in the 

 river or pond. 



The gravid female clams may generally be found by looking over material where 

 fishermen are at work. Unless the glochidia are sufficiently developed, the operation 

 is useless, for not until then will they open and close their valves when stimulated. 

 The fish are caught with the seine or net. 



From this it will be seen that the experimental shell-fish station and the fish- 

 cultural station go hand in hand. In fact it is a point of economy to combine the two. 



Although artificial infection would appear to be a comparatively simple operation, 

 a working knowledge of the process has only heen obtained as a result of careful and 

 laborious research. As yet only a few species of mussels are thus propagated. The 

 search for natural hosts is still being prosecuted. Experimental work is also being 

 carried on with the object of determining the period of parasitism, and the life history 

 of the young mussel after parasitism, and to lead to such improvements of methods 

 as will make the work most productive of practical results. 



It is interesting to note that within a period of two years, young mussels of 

 sufficient size to cut and finish buttons from their shells were reared at the station. 

 These were raised from artificially infected fish, which were kept in floating crates 

 or in earth ponds. They are not only the first mussels to be reared to such a size from 

 artificial infection, but they are the first commercial forms known to have been grown 

 in ponds. 



RESULTS OF ARTIFICIAL PROPAGATION. 



Although there is no means of definitely checking up the results of artificial pro- 

 pagation on a large scale, where the mussels already exist, yet the extent of the 

 confidence the United States Government has in the undertaking may be shown 

 by the fact that during the last fiscal year, 331,451,490 glochidia, in round numbers, 

 were liberated in the parasitic condition and 424,550 fish were employed in the opera- 

 tions. ^ It is believed that a considerable proportion of the glochidia fall upon 

 unfavourable ground, or fail to reach maturity from other causes. However, since a 

 large number can be liberated at a comparatively small cost, the attempt is deemed 

 justifiable. So far restocking, only, has been attempted, and in general fishermen 

 report that where artificial infection has been carried on, more young shells are found 



1 Annual Report of the Commissioner of Fisheries to the Secretary of Commerce for Fiscal 

 Year ended June 30, 1916. 



