FISH AND SHELLFISH AS FOOD 293 



sources of these essential amino acids. With the exception of the values for the 

 arginine content of shellfish and Crustacea the percentages of the 5 amino acids 

 determined are comparatively imiform for the diflFerent species. 



Inorganic Constituents. Clark and Almy's figures (Table 65) indicate that the 

 water-free substance of the flesh of the common marine fishes contains from about 

 3 to 7 per cent of ash. Data concerning the composition of the ash of a few im- 

 portant fishes as determined by Atwater (1892) and Riddell (1936) are pre- 

 sented in Table 73. 



Pike 7.38 3.81 38.16 2.50 23.92 20.45 4.74 



Source: Atwater, W. O., "The Chemical Composition and Nutritive Values of Food 

 Fishes and Aquatic Invertebrates," U. S. Fish Comm. Reft., 1888, 679-868 (1892). 

 Riddell, W. A., "Nutritive Value of Marine Products. XII Mineral Constituents of Some 

 Food fishes of British Columbia," /. Biol. Bd. Can., 2, 469^72 ( 1936). 



Nilson and Coulson (1939) determined the mineral content of the fillets (bone 

 and skin-free muscle) of a number of different species of fish. Their data are 

 summarized in Table 74 (p. 294). In general the mineral content of the fillets is 

 similar to that of beef round, except that beef contains more iron and much less 

 iodine. 



Newell and McCollum (1931) spectroscopically examined the ash of 7 species 

 of fish and found that all contained considerable amounts of calcium, iron, mag- 

 nesium, phosphorus, potassium, and sodium. Aluminum, chromivun, copper, lead, 

 lithium, manganese, and strontium were present as traces in all the species, while 

 fluorine, nickel, silver, tin, titanium, and zinc were present as traces in some 

 species and columbium and vanadium were doubtful. 



Tressler and Wells (1924) determined the iodine content of a considerable 

 number of marine and fresh-water fish, moUusks, and crustaceans. Clams, oysters, 

 and lobsters were found to be relatively high in iodine. Scallops, crabs, and most 

 marine fish were also found to contain far more iodine than fresh-water fish. 

 The results of their analyses are given in Table 75 (pp. 294-296). 



Composition of Shellfish and Crustacea 



The proximate composition of a number of different shellfish has been pre- 

 sented in Table 67 (p. 289). Some data concerning the amino acid content of 

 clams, crabs, oysters, and shrimp are given in Table 72 (p. 292). 



