Parathemisto libellula is common in the waters of the Arctic 

 structure. This species is eagerly eaten by planktophagous fish, par- 

 ticularly herring. In the northern regions of the sea, K libellula makes 

 up to 90% of the diet of the herring. Concentrations of P^. libellula with 

 a biomass of up to 250 mg/m3 have been reported in the northeastern and 

 Shantar Is. regions. In the central and eastern regions of the sea, P^. 

 libellula does not extend further south than 56°N, along the eastern 

 shores of Sakhalin it reaches as far south as 53°N, gradually submerging 

 from the surface layer to the 100-200 m layer. 



Thysanoessa rashii dominates among the euphausiids. In the fall, it 

 is encountered in the greatest quantities (up to 2500 mg/m3) along the 

 shores of Sakhalin and Kamchatka, particularly in the northwestern portion 

 of the sea (Ponomareva, 1959). In addition to these numerous species, 

 the oceanic cold-water community includes the copepods Derjuginia tolli and 

 comb- jelly Mertensia ovum . 



The main components of the oceanic cold-temperate community are 

 Calanus plumchrus , C^. cri status , Eucalanus b ungii , Metridia pacifica , 

 Parathemisto japonica , Thysanoessa inermis , and Th. longipes . C^. plumchrus 

 IS quite widespread and forms large concentrations in the surface 100 meter 

 layer. It, together with the euphausiids, is the basis of the diet of the 

 planktophagous fish. The maximum biomass of C^. plumchrus in the summer and 

 fall is found in the central region--up to 600-2000 mg/m^ (1959), though 

 it inhabits the northeastern portion of the sea in large quantities as 

 well. North of 57°N, the population of C^. plumchrus plummets rapidly. 

 C^. cristatus is encountered in largest quantities in the southern portion 

 of the sea, along the Kurile Islands, where its biomass in the 0-100 m 

 layer may reach 500-700 mg/m3; in the central portion of the sea, it is 

 not numerous. Eucalanus bungii is also scarce, its biomass reaching 200 

 mg/m3 (in the 0-100 m layer) only in the southern portion of the sea. 



Metridia pacifica extends throughout almost the entire sea, except 

 for its southwestern portion. The biomass is almost always less than 

 10 mg/m3, but sometimes reaches 200 mg/m3. The northern boundary of 

 large numbers of this species, like that of C. plumchrus , is at approximately 

 57°N. 



Thysanoessa longipes and T. inermis basically determine the biomass 

 of the euphausiids in the Sea of Okhotsk. The former species is encountered 

 in significant numbers along the coast of Kamchatka, and in the south of the 

 sea its maximum biomass--up to 3000 mg/m3--is observed in the spring in the 

 southern portion, in the summer and fall north of 55°N. T. longipes does 

 not form large concentrations, but is encountered almost throughout the 

 entire oceanic zone of the sea. The biomass of this species reaches 

 500-1000 mg/m3 (Ponomareva, 1963). 



The warm-water oceanic community in the Sea of Okhotsk is found only 

 in the zone of influence of the Soya Current, i.e., in the extreme south 

 of the sea, in La Perouse, Ecatherine and Vries Straits (Brodsky, 1955). 

 Characteristic species of the community are: Labidocera japonica , L^. 

 bipinnata , Candacia bipinnata , species of Euchaeta and Corycaeus , Evadne 

 tergestina , and salps. 



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