shark are rarely found in the Norwegian Sea). 



Large herring are almost Inaccessible to birds, excepting gannets , which, however, popu- 

 late only the southern zone of the Norwegian Sea . 



Within their entire feeding grounds, herring encounter no serious competition. Mallotus 

 villosus Cell . live farther to the north in the cold waters of the Greenland Sea and Spitsbergen 

 shelf. Cod, haddock, and roseflsh young are found mostly In the eastern branch of the Norwegian 

 current, in the vicinity of the slope . The biomass of these young fish is Insignificant as compared 

 with the number of herring feeding In that region. These young fish are herring food rather than 

 competitors of the herring. 



Mackerel are rarely found in the Norwegian Sea. The young of the blue whiting - Poutassou, 

 are encountered here more often than other fish and are distributed in a manner similar to that of 

 herring, but these fish are also scarce. In the southern half of the Spitsbergen current, as well as 

 in the region of Jan Mayen, we frequently found young salmon In drift nets . Young lumpfish may be 

 almost always observed in that region; these fish were carried away by the current in the zone of 

 Norwegian coast from some place and are drifting to the north, whence they are probably not 

 destined to retiim . 



Over the entire territory situated north from Thomson's Threshold and affected by the warm 

 Norwegian current, the herring are In reality the only numerous fish species utilizing the abundant 

 food resources of that region. We may say that over that entire vast territory the herring en- 

 counter no serious competitors and predators are scarce. Large herring perish during the period 

 of feeding migration to northern latitudes in considerably smaller numbers than during preceding 

 phases of development, wlien the herring are consumed by cod, Cololabls salra, roseflsh, and 

 numerous species of sea gull. 



ON THE PROBLEM OF DISTINGUISHING DIFFERENT SCHOOLS 



OF ATLANTIC -SCANDINAVIAN HERRING 



Atlantic-Scandinavian herring accomplish the most extensive migrations of all the herring 

 of the Atlantic and Pacific oceans. In view of this, the problem of Identifying different schools of 

 theserherring is extremely complex. We are now at the initial stage of the study of the above prob- 

 lem and It will take a considerable time to find an ultimate solution. 



Similarities In the living conditions within the limits of the range of Atlantic -Scandinavian 

 herring represent a serious obstacle to the establishment of sufficiently well-defined morphological 

 characteristics, which would enable the scientists to distinguish different races from each other. 

 So far, aU the attempts undertaken to that effect have failed (12, 36, 62). 



The divergencies in the growth rate of different schools of the ocean herring are very In- 

 significant, and it may well be that the errors of measurement exceed many times the actual diver- 

 gencies. The differences in the age composition of a school cannot be regarded as a criterion for 

 the study of different populations, since, on one hand, biological groupings of ocean herring lead 

 an Isolated existence and an analysis or a juxtaposition of the age composition of the school may be 

 provided only within the limits of such groupings, and, on the other hand, the analysis of age com- 

 position cannot provide us with the desired answer to the problem in view of the synchronous char- 

 acter of the phenomena of fluctuations in the case of Atlantic-Scandinavian herring within the bor- 

 ders of their entire range. 



47 



