blooming") usually coincides with the reproduction of Calanus . After the shedding of eggs, the 

 adults f)erish. In the plankton remain the microscopic nauplii of Calanus , which are unsuitable as 

 food for large herring. While feeding upon the pre-spawning concentrations of Calanus , the large 

 herring move northward at a quickened pace, "keeping ahead" as it were, of the "blooming". 



6. Plankton complexes, which are characteristic of the various biological seasons, can 

 exist at the same time in the various levels of the water where the Atlantic and polar waters mix. 

 Even during blooming, it is possible to encounter in such regions an abundance of Calanus and her- 

 ring. The latter feed upon the former . 



7 . The development or growth of diatoms in the Norwegian Sea coincides with the mass 

 production of young Calanus. 



The large herring leave for the north at this time. The young herring that feed upon red 

 Calanus , as a rule, do not form solid or compact concentrations (except regions with radical tem- 

 perature gradients). 



In regions with radical temperature gradients and, especially, If there is a cold or frigid 

 underlying layer, there occur compact concentrations of herring even when there is an abundance 

 of diatoms. 



8 . The observations in recent years have shown that the annual fluctuations in the time of 

 plankton production can cause a shift in the herring- feeding grounds. 



9. In view of the fact that the feeding migrations of herring are connected with the time and 

 the entire process of plankton production, we are compelled to study and analyze very thoroughly 

 the causes for the annual differences in the plankton production of the Norwegian and Greenland Seas . 



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