Figure 4. Population dlstxibution of Individual species of plankton during the summer of 



1953. 1. Themlsto llbellula; 2. Oithona simlUs ; 3. Pseudocalanus elongatus ; 

 4. Aglantha dlgltale; 5. Oikopleura labradorieosls ; 6. Themlsto abyssorum ; 

 7. Oncea bor calls ; 8. Euphausiacea . 



Th. llbellula Is the predominant species in the Greenland Sea. In the north central area of 

 the Norwegian Sea (in the Jan Mayen region and further north between longitudes 6 W and ) 

 Themlsto libellula and Th. abyssorum are found in the ratio of 3:1 at a salinity of 34. 60-34. 90°/oo 

 and a temperature of +0.55 to -1.7l"C. 



On the other hand, in the central areas of the Norwegian Sea in the 50-100 m. layer, where 

 the salinity is 35° /oo and more and the temperature is +3.47 to +3.86°C, the ratio of Th. llbellula 

 and Tn. abyssorum is 1:3, i.e. TK. abyssorum predominates (Figure 7 and Table 2). 



85 



