down to the 200-500-m. level and again 

 decreases at 1,000 m. : it is in general small, 

 a fact which corresponds to the isolation of that 

 sea both in the present epoch (shallow straits) 

 and in past times {complete lack of connections). 

 In the central part of the Arctic Ocean the num- 

 ber of Species is not great and there is a small 

 increase with depth which is related to the 

 thickness of the Atlantic stratum penetrating 

 the Arctic Ocean. Finally, for the northwest- 

 ern Pacific and the Japan Sea, lying in the 

 temperate zone, we can observe a definite 

 regularity consisting of a sharp drop in the 

 number of specimens with depth. 



The vertical distribution of copepods in 

 the northwestern Pacific Ocean, that is, the 

 sharp increase in the number of species with 

 depth, and the presence of a large percentage 

 of new species and of three new genera in that 

 region, naturally indicate the great significance 

 which a free interchange of water and fauna 

 with the whole World Ocean has for the deep- 

 water calanoid fauna. Significant in this con- 

 nection is the impoverishment of the fauna of 

 the dejths of such isolated basins as the Sea of 

 Japan and the central part of the Arctic Ocean. 



LITERATURE CITED 



BOGOROV, V. G. 



1946. Zooplankton fron-i the collections of 

 the expedition on the L/P "G. 

 Sedov" 1937-1940. Tr. Dreif. 

 eksp. na 1/p "G. Sedov" 1937- 

 1940. Main Administration of the 

 Northern Sea Route pub., 

 Moscow-Leningrad. V. 3. 



BRODSKII, K. A. 



194 1. On the plankton of the deep layers 

 of the Sea of Japan. Investigations 

 of the Far Eastern seas of the 

 USSR. ed. 1. 



1948. Free-living copepods (Copepoda) of 

 the Sea of Japan. Reports of the 

 Pacific Institute of Fisheries and 

 Oceanography, V. 26. 



1950. Copepods of the Far Eastern seas 

 of the USSR and the Polar Basin. 

 Keys to the Fauna, published by 

 the Zoological Institute of the 

 USSR Acadenny of Science, 35. 



JESPERSEN, P. 



1934. Copepoda. Godthaab Expedition, 

 1928. Meddelelser om Gronland. 

 Bd. 79, No. 10. 



Some Essential Features of Zooplankton 

 Distribution in the Northwestern Pacific Ocean* 



By 



V. G. Bogorov and M. E. Vinogradov 



The northwestern region of the Pacific 

 Ocean is a place of accumulation of a large 

 quantity of pelagic, plankton-feeding fishes and 

 a feeding ground for whales, the distribution of 

 which is closely tied to the distribution and 

 concentration of forage zooplankton in different 

 sections. However, the character of the dis- 

 tribution and the faunistic composition of the 

 plankton of the northwestern part of the Pacific 

 Ocean until very lately have remained little 

 studied. Just in the last few years Soviet and 

 foreign expeditions have begun to investigate 

 this region intensively. In 1949, 1953, and 1954 

 an oceanographic expedition of the Institute of 

 Oceanology worked there on the research vessel 

 Vitiaz'; in 1951, 1953, and 1954 investigations 

 were carried out by expeditions of the Institute 

 of Oceanology of the USSR Academy of Sciences, 

 for the study of cetaceans, and also by the 

 American Transpac Expedition (1953) and a 

 number of Japanese ships. The results of 

 working up the collections of the Transpac 

 Expedition have not yet been published. In 

 Japanese works, taking in the region oi the 

 Komandorsky Is. , the region to the east of the 

 Tsugaru Strait, and the region of the Bonin Is. 

 (Anraku 1954a, b), only the faunistic composi- 

 tion of the Copepoda is considered, and nothing 

 is said about the quantitative distribution of the 

 plankton. 



The materials gathered by the Soviet 

 Expeditions give a picture, not only of the 

 faunistic composition but also of the quantita- 

 tive distribution of the plankton. The results 

 of the working up of the collections made by the 

 expeditions of the Cetacean Laboratory of the 

 Institute of Oceanology in 1951 and 1953 have 

 been published in the works of K. A. Lubny- 

 Gertsyk (1955) and K. A. Brodsky (1955). In 

 the present paper we consider the distribution 

 of the zooplankton in the area from the Kurile 

 chain to 171°E. longitude and from the 

 Komandorsky Is. to 27°-30°N. latitude. 



The characteristics of the zooplankton are 

 given on the basis of the collections made 

 aboard the expedition vessel Vitiaz ' in August- 



*From Trudy Instituta Okeanologii, 

 Academy of Sciences of the USSR, Vol. 18, 

 p. 113-123. 1955. 



