730 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



This type of analysis provides us with an interesting scheme of the changes 

 in feeding groups of the sestonophages, detritophages and carnivores. The 

 replacement of one such group by another takes place not once but many 

 times. Within the Kuril-Kamchatka trench it occurs at depths of 3,000, 

 5,000 and 8,500 to 9,000 m (Fig. 354 and Table 298). Moreover, during the 

 replacement the group of biological phyla (according to their feeding) 

 remains the same, but the species may be quite different. 



Generally speaking detritus eaters are predominant, the plant-eating 



Continental 

 slope 



fl=/-5 



Ocean bed 

 'Slope into trench 



. 1 

 iverage depths 

 of trench КЛЛО| g 



_ 3 



I'-uiM/ Maximum cfep-fhs 



200 



3000 



5000 



7000 



9000 



- 10000 



Fig. 354. Correlation between benthos groups and bottom topography of the Ocean. 

 1 Sestonophage zone ; 2 Zone of a considerable development of all three feeding 

 groups ; 3 Zone of development of detritus feeders, either only roughly sorting the 

 soil or swallowing it whole A — Ratio by weight of detritus feeders to carnivores 



(Sokolova). 



species are absent from the deep-water fauna, and the deeper the water the 

 more pronounced this becomes. 



Among the crustaceans of the Far Eastern Seas the species Crangonidae 

 are carnivores (M. Sokolova, 1957). They feed on worms, crustaceans and 

 molluscs. Ophiuroidae form the main food of Sclerocrangon derugini. The 

 diet of the Crangonidae is most varied. 



Only a rough picture of the distribution of the bottom biocoenoses of the 

 northwestern part of the Pacific Ocean adjacent to the Kuril Islands and Kam- 

 chatka has yet been given (L. Zenkevitch and Z. Filatova, 1958) (Fig. 355). 

 Owing to the steep descent into the Kuril-Kamchatka trench, populated by 

 the ultra-abyssal biocoenosis of holothurians (Elpiidae), Pogonophorae 



