278 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



ABUNDANCE OF FOOD. 



That the nature of the food supply is a consideration of the utmost importance 

 requires no demonstration. The conditions which make an abundant food supply are 

 complex, depending upon density, temperature, and especially the supply of inorganic 

 materials in solution in the water. The bulk of the oyster food consists of diatoms, 

 which, although endowed with powers of locomotion, are nevertheless plants, and 

 acquire their nourishment from the same class of substances as do the common plants 

 about us. It is true that they have no roots penetrating the soil in search of saline 

 solutions, and they spread no broad foliage in quest of atmospheric oxygen and carbon 

 dioxide, but the whole plant is bathed in the nutritive sea water, from which they 

 receive their supply of liquid and gaseous food. If the water be impoverished of 

 salts the same adverse conditions obtain as in barren and exhausted fields and the 

 growth of plant life is in the same manner diminished. Now, how is the Gulf coast 

 situated as regards this inorganic material, indirectly, but no less imperatively, neces- 

 sary to the growth of the oyster? Along the entire shore line there are numerous 

 streams of all sizes which bring down mineral matter derived from the soil and nitro 

 genous substances from the decomposition of the rank vegetation of marshes, 

 swamps, and fertile fields. Some of these materials are in solution, and at once avail- 

 able for conversion into oyster food through the medium of the microscopic plants 

 already mentioned, but a large quantity is held merely in suspension, to be deposited 

 on contact with salt water and slowly passed into solution through the lapse of time. 

 With the abundance of food thus furnished, and nurtured by the warmth of semi- 

 tropical waters, it is not surprising that microscopic plant life should flourish. 



The rate of growth of the oyster depends upon the rate with which it is supplied 

 with food. When well fed its growth is rapid; when poorly fed its increase is slow. 

 In one locality an oyster may reach a growth of 6 inches in two years, and in another 

 place the same size is not attained under four or five years. On some of the more 

 profitable beds in Long Island Sound the latter is the case, while last summer, in 

 Plaquemines Parish, Louisiana, I saw oysters 6 inches long which, from known data, 

 could not have been over 23 mouths old and may have been slightly less, and then- 

 are doubtless many places on the Gulf coast where the growth is equally rapid. This 

 rapidity of maturation is an important matter to the oyster culturist. He is able to 

 receive quicker and greater returns for a given area and a given investment of capi- 

 tal, and his beds are less liable to disaster and recuperate more rapidly than if the 

 growth be slow. Large oysters are less readily covered by deposits of mud and sand 

 than smaller ones, and are more rarely destroyed by enemies, the latter usually proving 

 more destructive before the shells have become thick and the adductor muscle strong. 

 The drill is comparatively harmless to an oyster after it reaches a length of 3 inches, 

 and the starfish opens and the drumfish crushes large oysters with much less facility 

 than small ones. It follows that the mortality on a bed of well-grown oysters is less 

 than when they are small, and the more rapid the growth the less the death rate from 

 extrinsic agencies. The value which an oyster possesses in the market is dependent 

 largely upon its fatness and flavor, and both of these are principally and primarily 

 dependent upon its food. Oysters may reach a large size, yet not become fit for the 

 market, and in certain parts of the Atlantic coast the difficulty lias been keenly felt 

 by those engaged in oyster-culture. The United States Fish Commission is now 

 experimenting with a view to enable planters to fatten their oysters at will, but. deli 



