Eastern Part of Bering Sea 

 Position as to Biomass Type of Feeding 



Analysis of the composition of biologically homogeneous biocenosis 

 cores shows that their composition practically never includes more than 

 one species of the same genus--a rule noted by Elton (1946). Similar 

 species apparently have similar types of feeding, this similarity being 

 expressed not only in that they feed from a single source of food, but 

 also in that their method of capture of food and other peculiarities are 

 similar. In other words, similar species belong to a single life form 

 and occupy a single ecologic niche. Similarity of the nature of feeding 

 of closely related species is confirmed by the analysis of association 

 of two pairs of similar species ( Yoldia hyperborea and 

 Megayoldia thraciaeformis ; OphiurlTleptoctenia and 0. sarsi ) in the 

 eastern Bering Sea with types of bottom: The biocenoses of species of 

 each pair are found in this area on practically identical bottoms (Fig. 

 9). Competition in this case is avoided due to the spatial separation 

 of closely related species, which have different zoogeographic 

 association and inhabit zones where different water masses are in 

 contact with the bottom (Neyman, 1963a). The theory of parallel 

 communities is based on the spatial divergence of similar species 

 (Thorson, 1957) in which representatives of one life form, but with 

 different requirements for temperature or salinity, dominate. 



Thus, even an abundance of food, leading to the development of a 

 core of a biocenosis of species of the same trophic grouping does not 

 eliminate the need for the species to differ as to type of feeding. For 

 sestonophages, the possibilities for food differentiation are great, if 

 only because they can be rather finely divided as to levels. The 

 swallowing detritophages can also be divided in the same way--they can 

 feed from the bottom, burrowing into it to various depths. Gathering 

 detritophages do not have this capability--they can feed only from the 

 surfaces of the bottom. Therefore, difference in the nature of feeding 

 of gathering detritophages included in the core of a biocenosis must be 

 quite precise. This leads to yet another rule: The core of biocenoses 

 consisting only of gathering detritophages includes representatives of 

 only one zoogeographic or, in the language of G. V. Nikol'skiy (1947), 

 faunistic complex, probably because in order to achieve the precise 

 differentiations in feeding, long-term joint existence in the zone of 

 contact with the bottom of a single water mass is required. 



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