the pre-spawning concentrations of Calanus and Euphausiidae . 



We are inclined to assume or to accept that herring "avoid" the regions with great produc- 

 tion of Phaeocystis for the simple reason that they can not find food there . It is known that after 

 spawning, the mature Calanus die; but their microscopic nauplii are not fit as food for herring. 

 Furthermore, after the deaths of the spawned Calanus , the general biomass of plankton in the re- 

 gions that have the "green blooming" is greatly reduced. 



2. At the borders of the East Icelandic and the East Greenland currents, in the regions of 

 the polar front, where the simultaneous production of several plankton complexes that characterize 

 the different biological seasons occurs, the herring find food for themselves in the zone of the 

 "green blooming"; for herring concentrations can be encountered here also during the mass produc- 

 tion of Phaeocystis. 



3. The growth of diatoms coincides in time with the mass production of young Calanus and 

 does not interfere with the feeding or fattening of herring. Ehiring "diatom blooming", herring 

 usually feed over a large area and do not form solid schools or concentrations . 



Conclusions 



1. Atlantic -Scandinavian herring make feeding migrations into the northern latitudes of the 

 Norwegian Sea as well as to tae west and north-west into the polar or arctic waters. These migra- 

 tions are related most closely to the seasonal changes in the plankton production and distribution. 



Lengthy migrations provide the species with food, regardless of the flucttiations in the dates 

 of the development of plankton and its quantity . 



2 . The times when plankton develops depend on the intensity of the inflow of Atlantic waters 

 into the Norwegian and Greenland Seas, on changes in the hydrological, hydrochemical, and meteor- 

 ological conditions. 



The development of seasonal phenomena shifts from the shores of Norway into the regions 

 of greater depths, but also in a northern and north-western direction. 



3 . The herring of the older age groups that spawn in early spring usually penetrate far to 

 the north into the Greenland Sea . All the time they keep to the conditions that are characteristic of 

 the beginning of the biological spring. On the way, they feed upon the comparatively large crusta- 

 ceans that are getting ready for spawning. Their staple diet originates in the mixed Atlantic 

 waters near the cold or frigid masses of water of the East Icelandic current in the south and of the 

 East Greenland current . During the feeding or fattening period large herring can also penetrate 

 into the layers of the polar waters that were warmed up or heated by the sun at the moment of the 

 beginning of the biological spring there. 



4 . Herring that spawn for the first time approach the shores of Norway at a later date than 

 the older herring. At the time when they leave the spawning groimds, there appears in the plankton 

 a large amount, at first, of pink and, later, of red- -due to fat- -young Calanus . It is these fat 

 crustaceans that are the staple diet of young herring. The feeding migrations of herring that spawn- 

 ed for the first time, are considerably shorter than those of herring of older age groups . 



5. According to our observations, herring avoid the "blooming" when they cannot find any 

 food there. Most of the time, herring leave the southern and central coast regions of the Norwegian 

 Sea at the moment of the "blooming"; for there the development of the alga Phaeocystis ("green 



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