174 American Fisheries Society. 



Mr. Pope: Do you think it would be advisable, or have any experi- 

 ments ever been made to that end, to provide suitable food for the glochi- 

 dia other than living fish, thereby largely increasing the percentage of 

 glochidia that reach the adult stage? 



Mb. Canfield: We have no figures on the subject; there is no one 

 who could tell you definitely how many might be expected to develop 

 under those conditions. But it has been definitely shown that if the 

 mussel attains an age of six or eight months .there is very little likeli- 

 hood of its meeting with enemies, and the chances are that you would 

 get a very heavy percentage in that case. The greatest death rate is in 

 the juvenile stage, after it leaves the fish. Of course, the great trouble 

 in nature is that it would be more or less an accident if the proper host 

 fish should happen along just as the female mussel happened to release 

 the larval mussel. However, it is said that in some cases the mother 

 mussel attracts the fish to it by means of its waving cilia-like fringes. 

 But we do not know even that. I may say that in several plants that 

 we made, we recovered after two years practically one hundred per cent 

 of the mussels that we placed out, but these were not placed out until 

 they were about six or eight months old. With protection you could 

 place even the larval mussels out, but unprotected there would be con- 

 siderable loss. 



Dr. Osburn: Does the sheephead prey on mussels? 



Mr. Canfield : The sheephead is said to be an enemy of the mussel ; 

 both the sheephead and the catfish have been known to devour them, 

 also the pumpkin seed sunfish. I have no doubt that many fishes will 

 take them during the juvenile stage. 



Mr. Pope : Do you know of any experiments that have shown that 

 the glochidia are actually led by instinct to choose certain kinds of fish, 

 or is the fastening on a host an act of a mechanical nature? 



Mr. Canfield: It is entirely of a mechanical nature. 



Mr. Pope: Then why does it not take hold of the carp? 



Mr. Canfield : They do take hold of the carp ; they take hold of any 

 fish, but they do not remain on them — they are sloughed off or released 

 either by the fish or by the mussel prematurely. 



Mr. Burniiam: How do the protective laws protect the mussels? 

 Is it by providing a close season, or by limiting the size that may be 

 taken? 



Mr. Canfield: Mainly by closing certain areas alternately. For 

 example, at a certain place they would perhaps close the upper part of 

 the river for a distance of five miles, while the lower part of the river 

 would be left open, the idea being to allow clammers and others who are 

 engaged in the industry to continue their operations and at the same 

 time to permit the closed portion to recuperate. Then, at the end of 

 five years, which is regarded as a suitable length of time to allow the 

 mussels to mature, they will change about; the open area will become 

 closed and the closed, open. In that way it is planned to keep up the 

 industry and also the mussels. I have every reason to believe it is an ex- 

 cellent law. 



