and later 0.5 - 0.3 cm. a year. 



Increments in weight, which reflect the development of the organism more correctly, are 

 of greater interest to us . Following spawning, the weight of herring decreases markedly due to 

 the discharge of eggs and sperm from the gonads and to the reduction in fat content of the body 

 tissues. The fattiness factor becomes reduced to 1 and less. In the course of the summer feeding, 

 the weight of herring increases by 10-12 per cent and the fattiness factor rises to 1.1 - 1.2. In 

 Table 5, we present the minimum and average wei^t for herring of identical length at the end of 

 the reproduction period, prior to the beginning of feeding migration, as well as the mean and mini- 

 mum weight at the end of the summer, following the feeding season, and the fattiness factor. We 

 believe it correct to consider the fattiness factor of herring at the beginning of spawning migration 

 of herring as being equal to 0.95, i.e. somewhat below the mean index, since the number of her- 

 ring among the fish samples on the basis of which it has been estimated undoubtedly included certain 

 specimens that have already started feeding; for the herring, which completed the feeding, the 

 ratio may be considered as equal to 1.1. 



TABLE 5. WEIGHT AND FATTINESS FACTOR (kS PRIOR TO AND AT THE END OF 

 THE FEEDING MIGRATION. 



1) K= 100. P 

 L3 . 

 Knowing the mean indices of fattiness at the beginning and end of the feeding migration and 

 the growth rate of herring, we may draw the curve illustrating the gravimetric growth of Atlantic- 

 Scandinavian herring (Figure 5). Although it cannot be absolutely exact, it undoubtedly provides a 

 more correct conception of the increase of herring weight in the course of their life than the curves 

 customarily used demonstrating the growth of fish during different years . 



Young herring gain weight slowly. The drop in weight during the winter-spring season is 

 rather negligible and consists in the main in consumption of some negligible amount of fat reserves. 

 The maximum increments in weight occur in the 6th - 8th year of life, when herring still show a 

 good growth rate and the absolute volume of gonads is small. During the late period of their life, 

 the herring increase in weight considerably since the main energy is then used for restoration of 

 the gonads . 



During feeding migrations, the chemical composition of herring, fattiness in particular, 

 changes to a considerable extent. At the beginning of June, the fattiness-^of herring does not ex- 

 V In all these cases, we presented the overall fattiness, i.e. the fattiness of the given herring as 

 a whole. We used here the data provided by the Technical-chemical Laboratory of the Polar 

 Institute of Fisheries and Oceanography. 



36 



