THE BARENTS SEA 



97 



These females breed another summer generation. Moreover, Kamshilov notes 

 the considerable variation in the size of Calanus finmarchicus in the Barents 

 Sea, depending on temperature conditions. Large forms develop at a low 

 temperature, small ones at a high temperature. The large size, high breeding 

 capacity and other characteristics of the Barents Sea Calanus, do not enable 

 us, according to Kamshilov, to regard it as a special race different from the 

 Atlantic one. This difference between the data obtained by Jashnov and by 

 Kamshilov, separated by an interval of almost twenty years, might, possibly, 

 be explained by the warming-up of the Barents Sea waters. B. Manteufel 



1-Е-Ш 



PREDOMINANT STAGE 

 N Y 



ШШ8 

 ]9 



Fig. 35. Seasonal changes in number of specimens of certain age stages 

 of Calanus finmarchicus in southern part of Barents Sea (Jashnov). 

 1 Eggs; 2 Nauplius; 3 Copepodite stage /; 4 Stage II; 5 Stage III; 

 6 Stage IV; 7 Stage V; 8 Females; 9 Males. 



(1939) recorded a second generation of Calanus finmarchicus brought into the 

 southwest of the Barents Sea from the west. 



Calanus finmarchicus males never rise above the 75 m level, while the females 

 are more uniformly distributed. Late in the autumn and in the winter the grow- 

 ing Calanus finmarchicus go down to the deeper layers of the sea. 'Before the 

 coming of spring, ' writes V. Jashnov, ' Calanus finmarchicus begins to rise in a 

 mass into the upper layers, and the newly bred young stages begin to appear 

 then. ' Thus Calanus finmarchicus serves as a good example of a plankton 

 organism making seasonal vertical migrations during the year. 



The large pelagic crustaceans — Meganyctiphanes, Themisto, Thysanoessa 

 —have a biennial life cycle. Some of them breed twice a year, in the spring and 

 summer, others only in the summer. The picture of the vertical propagation 

 of these crustaceans is similar to that of Calanus finmarchicus : the immature 



