at stage V-VI. 



The mean stomach fullness index for the summer -spawning herring was 56.62; the food 

 contained 86% Euphausiacea and 14% young fishes. The herring of the second sample, with a mean 

 fullness index of 15.63, were feeding on Calanus finmarchicus (40%), Oikopleura and Themisto . 



At the end of July and during August, after feeding, the large herring form into groups and 

 begin to leave their northern feeding grounds for the southern areas, making their way towards 

 their winter quarters and next year's spawning grounds. 



For September, the data on feeding were collected In 1951 (samples 40, 41 and 42, Figure 

 4) and 1955 (Figure 5). All these samples of herring have a low mean index of fullness. Most of 

 the plankton had already sunk to the deep waters, and the herring were feeding on the scarce plank- 

 ton organisms which had still remained in the surface layer . 



In the beginning of September, Calanus finmarchicus constituted 91 .9% of the food of the 

 herring, whereas in the next samples (41 and 42) Calanus finmarchicus was a minor component, 

 with adult Euphausiacea and their young occupying first place . 



Two samples, 43 and 44, were taken in October 1952. According to these samples, the 

 principal diet of the herring consisted of Euphausiacea, Themisto abyssorum and Themisto comp- 

 ressa f. bispinosa. 



We have no data on the feeding of the Atlantic -Scandinavian herring during the winter months 

 of November, December, and January, but ship captains' reports to the Council for Marine Re- 

 search Vessels in January and February 1954 and 1955 give the following data: 



29th Jan. 1954 "Mature roe, some food in stomachs". 



20th Feb. 1954 "Herring having spawned, stomachs full of food". 



26th Feb. 1956 "Herring about to spawn, 70% with full stomachs (Euphausiacea)". 



From these data, it can be concluded that when food organisms are available the herring 

 also feeds during the winter months . The result of a field analysis also confirms that the herring 

 feeds during the winter months, althougji very little, a fact which was also observed by G. V. 

 Boldovskiy (3) in the case of the herring overwintering in the Barents Sea . 



Analysis of Food of the Herring and Composition of Plankton 



The principal food of the herring is plankton and young fish, but during the feeding period 

 not all the forms of plankton organisms are included in the diet . 



Hardy (14) notes that the entire community of plankton inhabiting the sea is not represented 

 in the food of the herring, and on the basis of this finding he concludes that the herring is capable 

 of selecting its food . 



Pchelkina (10), after comparing the different foods of the herring and the different forms of 

 plankton, notes two groups of animals which can be regarded as the favorite food of the herring 

 (Calanus and young Euphausiacea) . 



In order to determine the selective capacity of the herring, we compared the composition 

 of its food with the composition of the plankton obtained at checking stations during the drifting 

 season . 



154 



