while the females remain, as a rule, northerly from the concentration of males. 



PRE-SPAWNING CONCENTRATIONS OF ADULT HERRING AND 



THEIR ARRIVAL ON THE SPAWNING GROUNDS 



The main migration path to the spawning grounds passes across the western reaches of the 

 Norwegian Sea . A great number of herring return via the western edge of the western branch of 

 the Norwegian current. The exceptional importance of the latter course is due to the fact that 

 during the feeding season the main bulk of herring approaches the polar front, partially entering 

 the polar waters . On return migration, the herring keep close to the warm waters of the Atlantic 

 current, which probably serves as an orientation mark during the movement of herring to the 

 spawning grounds . 



We wish to point out that the migration paths to the spawning grounds coincide with the new 

 scheme of currents of the Norwegian Sea drawn by B. V. Istoshin and A. P. Alekseev. If a large 

 eddy existed in the central zone of the Norwegian Sea, the migration path of herring would probably 

 proceed towards the flow of Atlantic waters extending from Jan Mayen Island to the east towards 

 the shores of Norway . 



Ehiring the last few years , we succeeded in revealing the interrelation between the location 

 of the autumn migration paths and of the summer feeding grounds of the herring. The farther into 

 the Polar waters the herring schools penetrate, the more westerly are their migration paths and, 

 vice versa; the schools, which feed southerly from the polar front, proceed southwards via the 

 eastern zones of the sea. Thus, in 1952, a large adult herring concentration fed in the polar front 

 zone near Bank "600". Their path in September-October passed across the central zones of the 

 Norwegian Sea, somewhat westerly from the zero meridian. In 1954, the main bulk of herring fed 

 In polar waters. The 1954 migration path of herring was more westerly and passed in the vicinity 

 of the polar front . 



Despite the extensive research and large-scale reconnaissance operations that have been 

 carried out during these last few years, herring concentrations were found in the winter only in the 

 proximity of the East- Icelandic current. Wintering herring were spotted in 1952, 1953, and 1954 

 over a relatively small area, where at a depth of 50-80 m., there was a cold water layer below 

 2.5-3.5 C. We think it probable that this is not the only wintering region for adult herring and 

 that their presence and possibilities of fishing in that region are determined first of all by the cold 

 water layer which lies at a relatively shallow depth and prevents the herring from sinking to ex- 

 cessively great depths. In regions to the east of the Norwegian Sea, the cold layer is at a depth of 

 several hundred meters . In such conditions the herring are Inaccessible to present fishing methods . 



Predators and competitors of herring . 



During the season of feeding migrations, large herring are pursued by predators, but are 

 consumed by the latter in only insignificant quantities . After the large whales were exterminated 

 In the Norwegian and Greenland seas, the existence of herring became naturally much safer. Now 

 very few whales may be found. Bottle-noses (Hyperoodon) and killers (Orca) are also not numerous 

 and are the object of a small-scale fishing Industry conducted by Norwegian boats. More frequently, 

 herring concentrations are attacked by schools of white-sided dolphin ( Lagenorhynchus acutus) . 



Cod prey on herring only in the zone of the slope, but are rarely found at great distances 

 from shores or in regions of great depths; this is confirmed by the fact that only single specimens 

 of cod are found in drift nets . Cod are found in greater numbers in the Jan Mayen region (herring 



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