FISH AND SHELLFISH AS FOOD 297 



Composition of Roe. No complete analyses of the roe of marine fishes are to be 

 found. Atwater's analysis of shad roe is as follows: Water 71.25 per cent; water- 

 free substance 28.75 per cent; fats 3.78 per cent; nonnitrogenous extractive mat- 

 ters 2.56 per cent; protein (N X 6.25) 20.88 per cent. 



Gobley has examined the eggs of carp and determined the following sub- 

 stances: Water 64.08 per cent; paravitellin 14.06 per cent; fat 2.57 per cent; 

 cholesterol 0.27 per cent; lecithin 3.04 per cent; extractive matters 0.39 per cent; 

 coloring matters 0.03 per cent; inorganic matter 0.82 per cent. 



Greene (1921), who followed the chemical development of the ovaries of 

 the king salmon during the spawning migration, concluded that the mature ova 

 have a high content of protein. The protein is at least 70 per cent higher than 

 the yolk of the hen's egg, but on the other hand the lecithins and neutral fats are 

 less than half the amount stored in the yolk of the hen's egg. Greene's analysis of 

 mature salmon ova is given in Table 77. 



Table 77. Composition of Salmon Eggs. 



Total Water-free Fat-free 

 basis basis 



Per Cent Per Cent Per Cent 



Source: Greene, C. W., "Chemical Development of the Ovaries of the King Salmon 

 During the Spawning Migration," /. Biol. Chem., 48, 59-71 (1921). 



Nutritive Value 



Digestibility. Experiments on the digestibility of the protein of the edible por- 

 tions of fish by human subjects have indicated that from 90 to 96 per cent is 

 usually digested. The fat of fish is oily and usually easily and completely digested. 

 Holmes (1918) found that the digestibility of the fat of fatty fish varied from 

 86.4 to 95.2 per cent. 



Nutritive Value for Growth. Lanham and Lemon (1938) compared the proteins 

 from the edible portion of nine fishery products at a level of 9 per cent by weight 

 in the basal diet of rats. They found no practical differences in apparent digesti- 

 bility but noted that the proteins fell approximately into the following groups, 

 according to the relative growth-promoting value: 



100 90 80 63 



Oyster Pilchard Shad Beef 



Red snapper Cod 



Shrimp Croaker 



Boston mackerel Silver salmon 



Beveridge (1947) has recently determined the biological values of the crude 

 flesh proteins of fillets of ling cod, halibut, lemon sole, white spring salmon, red 

 snapper, and herring, and compared the results with data similarly obtained for 

 egg albumin and beef. The growth of rats brought about by the fish-flesh proteins 



