192 . BULI.ETIN OF THE BUREAU OF FISHERIES. 



allow them to enter upon the breeding season after being placed in the ponds of the 

 station. We have had females of different species of Quadrida become gravid in the 

 tanks of the laboratory after they had been held in confinement for weeks or even months, 

 and therefore no difficulty should be encountered in obtaining a supply of glochidia 

 from these forms under the conditions mentioned. 



REARING AND DISTRIBUTING YOUNG MUSSELS. 



After the fish have been infected, one of two things may be done in distributing 

 the young mussels resulting therefrom: Either the fish, after having been retained in 

 tanks or ponds until near the end of the parasitism, may be taken to the stream which is 

 to be restocked and the clams allowed to drop off there, or the liberation may take place 

 in ponds where the young mussels may be reared until they are of considerable size, 

 say until they are a year old, and then distributed as desired. Both methods might be 

 used successful!)', but in the first case it is to be supposed that only a very small pro- 

 portion of individuals thus liberated would succeed in reaching maturity, as they would 

 be exposed to the same destructive agencies as are encountered under natural conditions. 

 The difficulty and expense of transporting the infected fish, the mortality among the 

 fish themselves resulting from shipment, and the subsequent loss of large numbers of 

 the young mussels are considerations which lead one to regard this method as not an 

 efficient one. It should be stated, however, that in using this method of distribution 

 it would not be necessary to liberate the fish and thus lose them for subsequent infections, 

 for they could be confined in wire-bottomed fish cars set out in the streams, and after 

 the mussels had all fallen off' and dropped through the bottoms of the cars the fish could 

 be returned to the station. This would of course involve a very large amount of labor 

 and much expense. 



It would, therefore, seem to be a far more effective practice to retain the young 

 clams in ponds with natural bottoms until they could with safety be liberated in the 

 streams. After infection, in this event, the fish could be set free in these ponds at once, 

 and allowed to remain there throughout the parasitism of the glochidia, at the close of 

 which they could be seined out and made to do service again. Supplied with river 

 water, the ponds should furnish an adequate amount of food for a practically normal 

 rate of growth of the young mussels, which at the end of a year at latest should be of 

 sufficient size to be placed in favorable localities in the rivers. When ready for dis- 

 tribution, the water in the ponds could be drawn off and the juvenile mussels raked 

 carefully from the sand or mud. If properly packed, it should be possible to ship 

 them in large numbers to considerable distances. It is only reasonable to suppose 

 that a large proportion of the mussels thus reared would reach maturity after distribu- 

 tion, and it is certain that the number coming through would be far greater than would 

 be the case if the first method should be pursued. 



