■34 OYSTER BOTTOMS OF MISSISSIPPI EAST OF BILOXI. 



conditions to grow so rapidly and in such numbers as to completely 

 cover and stifle them. Also, as its food is the same as that of the 

 oyster, its abundance reduces the supply and in that way deprives 

 the oyster of the nutriment required to make it fat and marketable. 

 Even when neither of these effects are important, mussels injure the 

 fishery, owing to the tenacity with which they are anchored to the 

 oyster, which increases the labor of culling and makes the oyster so 

 unsightly from the adhering fibers of the byssus as to considerably 

 reduce its market value if sold as shell stock. The conditions 

 which make for the abundance of the mussel are not thorouglily 

 understood, but on the Gulf coast it appears to be controlled largely 

 by the saltness of the water, the mussels generally flourishing where 

 the salinity is low for prolonged periods. Comparatively few were 

 found in the region surveyed, and it is probable that they never or 

 rarely become troublesome on account of the high salinity frequently 

 occurrmg. 



Drumfish (Pogonias cromis). — This, the "black drum," was not 

 observed during the survey, but it is a destructive enemy of the oyster 

 in other parts of the Gulf coast and is reported to destroy oysters 

 on the adjacent beds of Alabama. It is migratory, making sudden 

 forays and leaving, with destruction m its wake, often before its pres- 

 ence has been noticed. It destroys the oysters by crushing them 

 between the stout grinding teeth or bones with which its mouth 

 is furnished, and it is peculiarly destructive to the better grade of 

 planted beds on which the oysters have been culled and separated 

 to permit them to grow and improve in shape and quahty. It is 

 especially hkely to attack the culled oysters within a few weeks of 

 the time when they are planted, but they are not immune at any time. 

 In Louisiana the drumfish is so destructive in places that the oyster- 

 inen find it necessary to exclude them by surrounding their bedding 

 grounds with wire fences. 



Oysters in the natural beds, especially when they are much clus- 

 tered and of the sharp-edged raccoon type, are rarely injured seri- 

 ously, as the sharp edges of the shells, presented in all directions, 

 lacerate the lips and mouth of the fish and deter them from exten- 

 sive destruction. Occasionally the small oysters culled off by the 

 oystermen are damaged. 



The drumfish occurs in waters of all degrees of salinity, from fresh 

 or practically fresh to full oceanic density. 



SPAWNING. 



The survey was conducted at the season when the reproductive 

 functions of the oysters are in abeyance, and therefore no definite 

 statement of the spawning season in Mississippi can be made. Vari- 

 ous investigations carried on by the Bureau at the western end of 



