movement of fish was assumed to be 10 km/day, of squids 15 km/day. 



One peculiarity of the model in question is that the elements of 

 the cells of the ecosystem are combined into groups. A group includes 

 elements with similar dimensions of individuals, type and spectrum of 

 feeding, and interaction with predators. Essentially, the organisms 

 combined into a group occupy a single, broad ecologic niche. However, 

 the reaction to abiotic factors, energy characteristics and 

 peculiarities of migration remain specific for each such element. This 

 separation of trophic groups greatly simplifies the modelling algorithm 

 and does contradict the biologic essence of the process being 

 modelled. The time step of functioning of the model was 5 days. 



Operation of the model began with an arbitrary initial state, 

 assuming even distribution of all elements of the ecosystem over the 

 water area of the sea. After three years, functioning of the model led 

 to a state which was near steady, in which the difference in the states 

 of the elements of the ecosystem for any given date of any two years did 

 not exceed 10%. 



The data, averaged over the entire surface of the Sea of Japan, on 

 monthly production of phytoplankton and zooplankton, bacteria and nekton 

 show that the production of phytoplankton has two rather sharp maxima. 

 The mean annual production of phytoplankton of the entire Sea of Japan, 

 according to the model, is 1,280 kcal/m^ per year--a quantity which is 

 quite probable, judging from the data of Yu. I. Sorokin and 0. I. 

 Koblentz-Mishke (1958). It is difficult to evaluate the likelihood of 

 the values of production of bacterioplankton and zooplankton obtained in 

 the model due to the lack of field determinations. The production of 

 the higher trophic levels (commercial fish and squid) can be compared 

 with their catch levels (Moiseyev, 1969). According to the model, the 

 annual fish catch (30% of the ichthiomass present), with a calorie 

 content of 1 kcal/g of wet mass, would be 820,000 tons for the entire 

 Sea of Japan, of squid--540,000 tons. The actual fish and squid catch 

 is about 1,000,000 tons, the potential possible catch--about 1.23 

 million tons (Gulland, 1970). 



The distribution of biomass of phytoplankton over the water area of 

 the Sea of Japan, according to the model data, is shown in Figure 7. In 

 the winter there are only small accumulations of phytoplankton along the 

 coast of Japan in the region of the Noto Peninsula and further south. 

 Intensive vernal development of phytoplankton occurs in Petr Velikiy Bay 

 and the entire central portion of the sea. By summer, the area covered 

 by accumulations of phytoplankton is reduced and is divided into two 

 areas--along the coast of Japan and Primor'ye. In the fall, the eastern 

 and central portion of the sea contains high phytoplankton biomass. 



Boreal epiplankton in the uper 200 meter layer is quite sparse 

 during the winter months. In the spring (March) the water area of high 

 concentration is significantly expanded and in the summer (July), the 

 area with a biomass of over 1 kcal/m^ covers almost all of the 

 northeastern portion of the sea, including Petr Velikiy Bay. 



336 



