Material and Method 



The present work is based on the material collected in the Norwegian and Greenland Seas 

 during the spring and summer of 1953 on the exploration vessel "Professor Mesyatsev" (E. A. 

 Pavshtlks) and the exploration vessel "Akademik Berg" by research workers of the Herring Labora- 

 tory. The work carried out in 1953 covers the area from the Faroes (latitude 60°N) to latitude 

 73°N. 



The material collected during 1951 and 1952 was used for comparison. Up to 1951, the re- 

 search work carried out by the "N. M. Knipovich" Polar Scientific Research Institute of Marine 

 Fishery and Oceanography (PINRO) was in the northern areas of the Norwegian Sea and in the south 

 of the Greenland Sea . 



Investigations in the southern and central areas of the Norwegian Sea were begun in 1951. 

 The number of stations and the number of plankton samples taken at each of them during the period 

 1951-3 will give an idea of the extent of the work. 



1951 1952 1953 Total 



Number of stations 415 382 246 1043 



Number of samples 708 741 664 2113 



The plankton was collected with a Nansen closing net of No . 23 gauze at the standard levels 

 (300-500, 200-300, 100-200, 50-100, 25-50, and 0-25 m.). 



Some of the specimens consisted only of the total catch from bottom to surface, which makes 

 it difficult to determine not only the depth at which a particular organism lives but also its relation 

 to temperature and salinity. 



The most valuable material is that collected by E. A. Pavshtiks, who 'fished' the 10-25, 

 5-10, and 0-5 metre levels in addition to the standard levels. This gives the fullest picture of the 

 vertical distribution of plankton organisms . 



It should be noted, however, that Nansen's net is not efficient for catching nanoplankton 

 (the smallest forms) or actively swimming plankton organisms, especially the higher crustaceans - 

 Euphausiacea . Consequently, no quantitative calculation of plankton cau^t with a Nansen net is 

 very reliable. 



The complete analysis of the collected material was made at the Laboratory. The species 

 of the plankton organisms were identified with the aid of a Reichert binocular microscope. The 

 quantity of organisms was determined visually according to the scale: 'occasional specimens', 

 'very little', 'little', 'moderate quantities' and 'large quantities' - which corresponds to the five- 

 mark system. In order to be able to compare the material, the plankton spjecimens were weighed 

 and the crude weight was converted into mg/m^. i-e- the biomass of the plankton was calculated 

 for the 0-50 m. layer. 



Charts showing the distribution of warm -water and cold-water organisms, graphs of plank- 

 ton distribution in dependence on temperature, and charts of individual plankton populations in 

 different years were then prepared. 



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