COMPOSITION OF FISH 349 



fish generally contain less trimethylamine oxide than marine fishes, with 

 amounts generally in the range 5 to 20 mg per cent. 



Freshly caught fish generally contain only a very small part of their 

 amino acids in the free form, although free amino acids may form post 

 mortem in a very short time after the fish are caught. An exception occurs 

 in tuna which has an unusually high content of free histidine in the flesh. 



Urea occurs in elasmobranch fishes in fairly high amounts. In sharks 

 and rays, the urea content may amount to 2 per cent of the flesh. In the 

 teleost fishes urea occurs in quantities of only about 0.05 per cent. 



Creatine occurs in teleost and elasmobranch fishes in about equal 

 amounts, averaging about 0.5 per cent in the wet muscle. Carnosine 

 occurs to an extent of about 0.1 per cent to 0.4 per cent and anserine 

 about 0.04 per cent. 



The principal carbohydrate occurring in fish is glycogen, averaging 

 about 0.6 per cent maximum. When the fish has undergone severe strug- 

 gling just prior to capture, a lactic acid content of several tenths per cent 

 may occur and the glycogen content will be reduced accordingly. Free 

 glucose occurs in fish in concentrations in the range of 1 to 75 mg per cent. 



LITERATURE CITED 



1. Malins, D. C, Chem. and Ind. 1960, 1359(1960). 



2. Olcott, H. S., Shuster, C. Y., and Froines, J., Proceedings F.A.O. Conference on 



Nutrition in Fish, September, 1961. 



3. Olley, J., and Lovern, J. A., Biochem. J. 67, 610(1954). 



