574 



MARINE PRODUCTS OF COMMERCE 



show that a single portion consisting of 6 raw Atlantic oysters, weighing approxi- 

 mately 3/2 ounces, contains the following nutrient factors: 



According to these data one serving of raw oysters will supply more than the 

 daily allowance of iron and copper, about one-half of the iodine needed, and 

 about one-tenth of the daily requirement of protein, calcium, phosphorus, vita- 

 min A, thiamine, riboflavin, and nicotinic acid (Radcliffe, 1947). 



By-products 



Oyster shells from shucking houses are used for road construction and for man- 

 ufacture of poultry food, and are burned for lime. During World War II the newly 

 developed plants for the extraction of magnesium from sea water used very large 

 quantities of oyster shell as a source of lime needed for the precipitation of mag- 

 nesium hydroxide (Chap. 4). 



In 1948 the United States produced 345,075 tons of oyster and marine clam 

 shell products, valued at $2,474,492. The shells to be used for poultry "grit" are 

 first dried in a heated rotary drier, then crushed, screened to various sizes, and 

 packed in bags. 



Large quantities of so-called mud shell (i.e., shells of dead oysters buried in 

 mud) are dredged from Texas waters and are used by the manufacturers of 

 lime and poultry foods. The demand for oyster shells is so great that oyster grow- 

 ers frequently experience difficulty in obtaining the cultch they need for planting 

 on their grounds; thus, lack of shells in some of the Atlantic States constitutes 

 a serious handicap to the progress of the oyster industry. Because of the inade- 

 quate supply of shells for planting attempts were made to use diflFerent substi- 

 tutes. The most promising is probably the slag from steel plants. Experiments 

 carried out in Delaware Bay and in Maryland waters showed that slag may be 

 used instead of shells to catch seed oysters. It presents, however, several disad- 

 vantages due to its weight, shape, and other characteristics. So far the oyster 

 shells remain the most practical material to be used in the cultivation of oysters. 



REFERENCES 



Anderson, A. W., and Power, E. A., "Fishery Statistics of the United States, 1945," 



U. S. Fish and Wildlife Ser\'ice, Statistical Digest, 18 (1949). 

 Awati, P. R., and Rai, H. S., "Ostrea cuciillata (the Bombay Oyster)," Lucknovv, India, 



The Indian Zoological Memoirs III (1931). 

 Bergmann, W., "Contributions to the Study of Marine Products. Ill: The Chemistry of 



Ostreasterol," /. Biol. Chem., 104, 553-557 (1934). 

 Brooks, W. K., "The Oyster," Baltimore, Johns Hopkins Press, 1905. 



