Mesyatsev". 



In the early part of April, we worked near the Norwegian shores and in the Lofoten shallows, 

 where at that time the spawning of herring of the older groups was coming to an end. Their larvae 

 were found in the plankton . 



In the shallow waters, the plankton was poor, the "blooming" was beginning and the post- 

 spawning herring were leaving these regions for the Atlantic waters . In the latter part of April, 

 the "blooming" included the Norwegian current near the continental shelf. Keeping ahead of the 

 "blooming", the herring continued to leave for the north and north-west. 



There is a heavy production of tlie "green blooming" ( Phaeocystis ) in the shallow waters and 

 in the waters of the eastern branch of the Norwegian current. In the latter part of April, only iso- 

 lated small spots of the Phaeocystis "blooming" could be observed. But during the first ten days in 

 May, a considerable area had a great "bloom". The herring moved into the deep water, where the 

 biologfical spring is somewhat delayed. In the second half of May, the Phaeocystis "blooming" was 

 observed north of 70° north latitude (between the arms of the current) and in the region of vortexes 

 or eddies at the borders of the East Icelandic current, between Jan Mayen and the Faroes. 



What then caused the herring to leave or abandon the coast regions, to "avoid" the "bloom- 

 ing" that was brought about by a great development of Phaeocystis ? 



We are inclined to assume that the herring left the coast and shallow water regions in 

 search of food. After spawning, the exhausted herring begin to feed ravenously on the pre-sp)awn- 

 ing concentrations of Calanus finmarchicus . The spawning of these crustaceans coincides with the 

 beginning of phytoplankton production. Having spawned, the Calanus finmarchicus die, but the 

 Euphausiacea leave for the deep. Due to this, the herring fail to find sufficient food for themselves 

 and quickly shift to other regions. 



Usually one can observe three phases in the development of Phaeocystis . 



The beginning of the "blooming" of Phaeocystis is heralded by encountering a greenish sedi- 

 ment and large spawning Calanus in the plankton sample. The algae develop in the upper layer of 

 the water (to a depth of 15-25 m.). 



At the hei^t of the "blooming", the amount of the greenish slimy sediment in the plankton 

 samples greatly increases. Large mature Calanus are seldom encountered in the samples; there 

 appear many eggs and nauplii of crustaceans. 



At the end of the "blooming", brownish -green flakes of dying algae and large numbers of the 

 small young of Calanus appear. When dying, the algae sink into the deep, but the herring (usually 

 young) remain at the surface, where they feed upon the young Calanus . 



In the developing "blooming", herring descend to a depth of more than 20 m. and head for 

 the outside limits of the "blooming" where they usually find suitable food. 



We are of the opinion that it is only the lack of planktonic food, instead of the great Phaeo - 

 cystis production (for the nauplii of Calanus , because of their microscopic size, cannot be used as 

 food by herring) that compels the herring to abandon the zone of "blooming" for waters that abound 

 in plankton that is fit for food (Figure 14). 



For instance, our observations at station No. 108 on June 16, 1953, indicate that Phaeocystis 



131 



