Warm Atlantic waters penetrate as far as Jan Mayen via the latter branch. 



The second- -eastern (or continental)- -branch proceeds to the north-east along the continen- 

 tal slope. Its direction corresponds to the scheme of Helland -Hansen and Nansen. In the process 

 of investigations of the Polar Institute, the hydrological importance of the underwater relief of the 

 Norwegian and Greenland seas, particularly to the east from Jan Mayen, where underwater eleva- 

 tions of volcanic origin were discovered, has been established. The chain of ancient volcanoes 

 extends from Jan Mayen to southern Spitsbergen. 



In the region of these sea mounts, the vertical waters circulation is very strong, which 

 creates favorable conditions for plankton development. Moreover, drastic temperature fluctu- 

 ations on the slopes of the elevations contribute to the concentration of herring in these regions . 



The polar front zone is relatively constant, adapted to the ocean floor topography to a 

 greater extent. The polar front extends from Jan Mayen to the south, along the underwater chain 

 of mountains proceeding in the direction of the Faeroes and to the north-east, along Mohn's 

 Threshold. 



Thus far, the migration paths of herring have been studied only in isolated regions of the 

 North-European basin. 



In 1951, we followed the drift of herring schools which had completed spawning, along the 

 eastern branch of the North Cape current from the south-western shore of Norway up to the latitude 

 of the Lofoten Islands. In 1952, the migration of herring via this particular course was not as 

 clearly pronounced. The majority of schools moved to the north via the western branch of North 

 Cape current across the Helgoland Ridge and in the direction of Bank "600". Furthermore, we 

 located the movement of herring along the eastern edge of the East-Icelandic current. That path 

 led the herring to Jan Mayen and Bank "774". A relatively insignificant movement of herring in the 

 western direction was recorded in 1953 during the cruise on board the exploration boat "Professor 

 Mesyatsev" along the southern border of the East- Icelandic current. That latter course probably 

 leads to the eastern coast of Iceland. 



The movement of herring concentrations into the region of the polar front is illustrated in 

 Figure 6. The pointers show only relatively large concentrations, the location and direction of the 

 movement of which have been verified by exploratory or reconnaissance boats . The majority of 

 these concentrations were intensively fished. 



During the third cruise of the scientific research boat "Professor Mesyatsev" in 1953, we 

 succeeded in observing the arrival of herring in the zone of the polar front and the movement of 

 schools into the polar waters, where the temperature conditions at the surface hardly differed 

 during that season from Atlantic waters (6-7°). In polar waters, the herring remained near the 

 surface, since at the depth of 25-30 meters we noted that the temperature dropped drastically. Be- 

 neath that depth, the temperature was at sub-zero level . 



At that time (middle of July), certain schools of herring were found at a distance of 50-60 

 miles from the polar front. The schools were very dense, and the fishing was very successful: 

 certain boats obtained as much as 25 to 30 tons of fish per drift . 



Herring began leaving the polar waters in the second half of July and continued moving away 

 throughout August . 



A considerable number of adult herring were feedingin 1954 west and north-west of Jan Mayen 



39 



