NUTRITIVE VALUE OF FISH AND SHELLFISH 



517 



si.sting mainly in the slight loss of moisture where the cooking takes 

 place imder dry conditions and, on the other hand, a loss in nitro- 

 genous or protein material where the fish are boiled. The main 

 object in cooking fish is to make them palatable in accordance with 

 the tastes of civilized man. It should be noted, however, that many 

 of the native tribes and many of the people in civihzed countries do 

 eat fish raw. In Japan it is cjuite customary to eat fish flesh vvithout 

 cooking, but in Europe and America it is usually only pickled herring, 

 smoked salmon, etc., that are eaten without any real cooldng by heat. 



VARIATIONS IN THE COMPOSITION OF FISH 

 SEASONAL AND MATURITY VARIATIONS 



It has already been mentioned in connection with the discussion 

 of Tables 2 and 3, giving the general composition of food fishes, that 

 very marked variations occur in the composition of fish. These 

 changes may be roughly classified as due to (a) season or maturity, 

 (6) locaHty, (c) variations in individuals, and {d) variations in the 

 different parts of the body of the same fish. In this section the 

 seasonal and maturity variations only wiU be discussed. 



In Table 11 Dill (i921) presents the analyses at different times of 

 the year of some important economic fishes of the mackerel family 

 caught off the coast of California. 



Table 11. — Analyses of various fishes of the mackerel family caught off the coast 



of California 



[Analyses of the edible portion on the fresh basis] 



In the case of the albacore, for instance, which is so important for 

 canning purposes, it will be seen that the percentage of fat, which 

 so largely influences the fuel value, seems to reach its peak about 

 the first week in September and then falls off again during October 

 and November. Expressed in terms of fuel value, the albacore 

 caught early in the season averaged about 690 calories per pound, 

 while those caught the first week in September averaged 986 calories 

 per pound. Later on in the fall the fuel value dropped down to an 

 average of 750 calories. We find the same thing illustrated in the 

 analysis of the yellowfin tuna, where the fat content seems to reach 



