THE FOOD VALUE OF FISH 



117 



that is whether it is spawning or not. Further, it may 

 be considerably modified by the changes that take 

 place subsequently in the composition of the flesh during 

 the processes of curing, cooking or preserving. 



Generally speaking, all marine fish annually pass 

 through a well-marked series of seasonal changes, the 

 stages of which appear to depend upon changes in the 

 temperature, salinity and alkalinity of the sea. These 

 changes are directly connected with the development of 

 roe and milt, with the fluctuation in the percentage of 

 oil and fat in the liver and body tissues, and also with 

 the rate of growth. Thus the chemical composition 

 of the fish, and hence its food value, varies greatly 

 according to the season at which it is caught. 



Norwegian brisling (" Skipper Sardines ") are caught 

 in the summer just before spawning time. At this 

 time the fat content is high ; in winter the fat content 

 is low, and the fish possesses small commercial value. 



The gradual change in the composition and food 

 value (in calories per pound) of the herring as spawning 

 time approaches is well shown in Table III. (Prof. 

 J. Johnstone, Trans., Liverpool Biolog. Soc., Vol. xxxiii 

 (1919), p. 106.) 



TABLE III 



MANX SUMMER HERRINGS, 1916 

 COMPOSITION OF THE FLESH OF THE FISH : MONTHLY MEANS 



