OYSTER BOTTOMS OF MISSISSIPPI SOUND, ALA. 55 



expected, their inroads appear to have been coincichnit with periods 

 of prevalence of highly salt water on the beds. 



The drill or whelk lays its eggs in red or purple leathoiy capsules 

 about one-half mch long and attached in clusters to shells, snags, and 

 other firm bodies in the water. The young become destructive to the 

 minute spat immediately on emerging from the egg cases, they grow 

 rapidly, and progress m destructivcness as they increase in size. They 

 destroy the oysters by drilling a small round hole through the shell, 

 usuig for the purpose a flexible rasp-like organ lying at the end of a 

 protrusible proboscis. After the shell is perforated the proboscis is 

 thrust into the shell and the contents eaten, other drills sometimes 

 partakmg of the feast by entering the gaping shell of the dead or 

 dying oyster. Most of the oysters destroyed are under 2 inches long. 



Mussels. — The common black sea mussel is a passive enemy of 

 oysters through its tendency to attach to them and under favorable 

 conditions to grow so rapidly and in such numbers as to cover them 

 completely 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 nutrunent requu-ed to make it fat and marketable. 

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

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

 oyster, this increasmg the labor of culUng and makmg the oyster so 

 unsightly from the adhering fibers of tlie byssus as to considerably 

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

 make for the abundance of the mussel are not thoroughly understood, 

 but on the Gulf coast it appears to be controlled largely by the relative 

 freshness of the water, the mussels generally flourishmg 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 

 occurring. 



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

 observed durmg the survey, but it is a destructive enemy of the 

 oyster in other parts of the Gulf coast and is reported to destroy oys- 

 ters on the beds of Alabama. It is migatory, making sudden forays 

 and leaving, with destruction in its wake, often before its presence 

 has been noticed. It destroys the oysters by crushmg 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 quality. It is especially likely 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 oystermcn find it neces- 

 sary to exclude them by surrounding their bedding grounds wdth wire 

 fences. 



