lower than in central and southern regions (Fig. 2). Deep-water 

 stations ofthe region (Stations 7, 1 l.and 15)showedacopepod 

 accumulation density of 330,000 ind/m-. Most probably, 

 conditions of the shelf waters of the Bering and Chukchi Seas 

 exert a negative effect on population development. In the Gulf 

 of Anadyr, western regions of Chirikov basin, and in Bering 

 Strait as well as in the Chukchi Sea, population abundance did 

 not exceed 50,000 ind/m-. 



Figure 3 shows the character of distribution of levels ofthe 

 Pseudocalanus niinitus population. This species is most 

 developed in the northwest regions of investigations in the 

 Chukchi Sea were the number of P. minutus population reached 

 470,000 ind/m-. In general, the population of the shallow 

 regions of the Chukchi Sea is two to three times more than that 

 of the Bering Sea pelagic zone. The scattered character spatial 

 location of populations and different sizes of copepods, which 

 are bigger in the Chukchi Sea and smaller in the Bering Sea, 

 suggest that there are at least two separate populations inhibiting 

 the Bering and Chukchi Seas. The size of the Bering Sea 

 population of P. w(>7i<r«5 varies from 13 to 20,000 ind/m-; there 

 was no significant difference between density of deep-sea and 

 shelf accumulations. We should note that there was a 

 coincidence of regions of the Bering Sea with decreased 

 abundance of P. minutus and O. similus total numbers. 



There was a similar distribution pattern of Aglantha digitale 

 (Fig. 4). Their numbers varied from 10 to 4,000 ind/m-. 

 Developmental peaks of this species were determined by water 

 masses situated over the depth gradient in the northwest Bering 

 Sea, shallow regions of eastern Chirikov basin, and Bering 

 Strait, and northwest center of the Chukchi Sea. Centers of 

 accumulation of populations ofthe appendiculari an OfA^op/ewra 



number, ind/m" 

 in 0-100 (botlomi 

 layer 



Fig. .V 



labradoriensis were found in the Bering and Chukchi Seas on 

 the shelf. Waters of these seas are characterized by extremely 

 low temperatures. Thus maximal abundance, over 

 300,000 ind/m-, was found in the western Chukchi Sea that is 

 subjected to the effect of cold arctic waters. It should be noted 

 that the location of most numerous groups of appendicularians 

 coincides with the region of lowest density of copepods 

 (O. similis and P. minutus). The abundance of this species in 

 the epipelagic zone of the Bering Sea deep-water regions did 

 not exceed 1,000 ind/m- (Fig. 5). 



number, md/m- 

 in 0-100 (bottom) 

 layer 



Distribution of Pseudocuiunus imnulus in thie northern Beting and 

 southern Chukchi Seas. 



Fig. 4. Distribution oi Aglantha digitale in the northern Bering and southern 

 Chukchi Seas. 



Another species of appendicularians, Fritillaria borealis, 

 resembled the distributional pattern of O. labradoriensis and 

 was found only in shelf water plankton of the Bering and 

 Chukchi Seas (Fig. 6). Still, the boundary between regions 

 with favorable and unfavorable conditions for Fritillaria 

 borealis was situated much farther to the north, along the 

 boundary of the central shelf region of the Chirikov basin. The 

 highest number of F. borealis in the central basin equaled 

 300,000 ind/m-. The number of this species in the Chukchi Sea 

 did not exceed 90,000 ind/m-. 



Species of the south Bering Sea oceanic group showed a 

 similar distributional pattern in the study area. As northbound 

 oceanic waters drifted across the shallow shelf region, the 

 number of species ofthe complex decreased gradually, reaching 

 its minimum in the southern Chukchi Sea. They were transported 

 via the western Chirikov basin and the Bering Strait. 



165 



