chance to advance far into the north. 



The small percentage of herring with empty stomachs (18% in the north and 74% in the south- 

 ern part of the Norwegian Sea) emphasizes the favorable feeding conditions for herring in July in 

 the areas north of Jan Mayen.— ' 



In 1954, the herring stopped feeding in the northern regions in August. 



In 1955, the herring continued to feed until the end of September. The reason for this was 

 found in adate biological spring (plankton production, in contrast with 1954, began 30 days later). 



Under the influence of unfavorable hydro -meteorological conditions, (a large number of 

 storms, murky days, and a general drop in the water temperature) the spawning of Calanus and the 

 appearance of its fat red young was greatly delayed. The herring then- -as a compensation for the 

 lack or shortage of Calanus - -turned to the young of Olkopleura labradoriensis and T hemisto abys - 

 sorum. Herring of the older age groups entered the waters with a temperature of 2-3 as early as 

 June and fed there upon the concentrations of the spawning Calanus hyperboreus . 



In the area of Mohn's Threshold, red Calanus did not appear in 1955 until July and remained 

 in the surface layers until the end of August, A general decrease in the intensity of the inflow of 

 Atlantic waters (this accounts for the almost entire lack of the thermoiMlic organisms of Collo- 

 zoum, Tomopteris, Physophora hydrostatica in plankton) delayed the development of jellyfish, 

 which usually feed on the plankton. 



The conditions outlined above had a favorable influence upon the feeding or fettening of her- 

 ring. There was enough food for all the herring. They fed regularly during four months (June-Oct- 

 ober) and, regardless of the partly empty stomachs, the herring had become sufficiently fat by 

 September. 



Thus the observations of recent years have established that 1) during the time of the spring 

 and summer feeding the herring of the older age groups inhabit the greatly transformed Atlantic 

 waters--often close to cold currents --where they usually find a good feeding area composed of re- 

 producing, comparatively large Crustacea; 2) a change in the intensity of the Inflow of Atlantic 

 waters in different years influences to a certain extent the times of the production of plankton in the 

 Norwegian and Greenland Seas as well as its species composition and its amount. 



According to our observations the intensity of the North Cape current and of the eastern 

 branch of the Norwegian current changes asynchronously. This is due, perhaps, to the feet that in 

 some years more warm water enters the western regions of the Norwegian Sea, whereas in other 

 years more warm water enters the eastern regions and the Barents Sea. 



When the intensity of the inflow of Atlantic waters into the Norwegian Sea is lessened as well 

 as when a lessening of radiation heating of the surface water layers occurs, then the biological 

 spring is usually delayed, Calanus develops later and remains for a longer period in the surfece 

 layers, which is a favorable condition for the feeding of small herring. Furthermore, a general 

 slackening in the water circulation brings about an increased temperature of the mixed waters and 

 an earlier development of plankton in them. This facilitates the feeding or fettening of older her- 

 ring there . 



In warm years when there is a general acceleration in the circulation of Atlantic waters, an 



early biological spring can be observed in the Norwegian and Greenland Seas. 



\J Material by Rudakova, V. A. 



128 



