Figure 1. --Distribution of the basic plankton complexes. 1 - boreal region; 

 2 - transition zone; 3 - tropical region; 4 - stations of the research ship 

 Vitiaz' in August-October 1954; 5 - stations of the expedition of the 

 Cetacean Laboratory in August-September 1954. 



Beyond the coastal waters, with their low 

 zooplankton biomass, is spread a zone of high 

 biomass. This zone extends along the Kurile 

 Islands in a belt of varying width, usually not 

 wider than 30-50 miles. In May-June 1953 the 

 plankton biomass in this zone at 0-100 m. con- 

 stantly exceeded 1, 000 mg. /m. ^. In August- 

 September 1954 it was somewhat lower, and 

 varied from 500 to 1, 000 mg. /m.^. Thus the 

 quantity of zooplankton declined, but the location 

 of the zone of highest biomass did not change. 

 Approximately the same area was also richest 

 at the end of July 1951 (Lubny-Gertsyk 1955). 

 South of the Kurile -Kamchatka Trench the 



plankton bionnass in the upper 100-meter layer 

 in May-June 1953 decreased to 500-1,000 

 mg. /m. , but in August-September 1954 to 250- 

 500 mg. /m. , i.e. approximately to one-half. 

 Still farther south, approaching the boundary of 

 the boreal region, it quickly falls to 100-250 

 mg. /m.^ in August-September. 



In the region lying east of Tsugaru Strait 

 the quantity of plankton is relatively great: 

 from 250 to 500 mg. /m. . But in its composi- 

 tion it differs from the plankton of the zone of 

 the Kurile-Kannchatka Trench in that along with 

 the species of the boreal region there appear 



