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



part of the Sea the bottom fauna plays a considerable role. This consists 

 mainly of bottom crustaceans (about 5 per cent), Hyas araneus, Eupagurus 

 pubescens and different Amphopoda, Isopoda and Cumacea. Among the 

 other invertebrates (about 5 per cent) the most important are the molluscs, 

 echinoderms and polychaetes. Cod feeds also, to a small extent, on bottom 

 fish (about 4 per cent), on long rough dab, goby, launce and others. In general 

 more than 200 species of different creatures have been found in the stomachs 

 of cod. 



Although omnivorous, cod always prefers fish which is its main food. 

 Pelagic crustaceans act as a substitute diet, since in the presence of herring or 

 caplin cod would always feed on them. With that exception, the diet range of 

 cod reflects, to a considerable degree, the quantitative ratio of various groups 

 of organisms present in water. 



The quantitative ratio of the different components of the cod's diet is 

 very stable, as is obvious from a comparison of annual data for several years 

 {Table 70). 



Table 70 



Food composition of cod in 

 groups, per cent 



Group 1939 data 1934-38 data 



In the course of a year cod feeds differently in various parts of the Barents 

 Sea, so that a regular annual cycle is obtained (Fig. 65 and Table 71). In early 

 spring (February-April) after slowing up during the winter, cod begins to 

 move eastwards (Fig. 64), feeding intensively on pelagic fish — herring and 

 caplin. The cod which have spawned off Lofoten arrive rather later and like- 

 wise feed on fish. In summer in the central commercial fishery areas it feeds 

 on the higher crustaceans (Euphausiacea and Hyperiidae). In autumn cod 

 assembles in shoals in the eastern parts of the Sea, and in the absence of her- 

 ring and caplin, turns quite extensively to bottom food — large crustaceans 

 such as crabs and hermit crabs, and molluscs. While starting its westward 

 movement cod reverts to a diet of fish (the young of both cod and haddock, 

 herring, caplin). Those cod which travel westward to spawn in the Lofoten 

 region (January- April) stop eating, at first partially and then completely ; off 

 Lofoten they are always caught with empty stomachs. The young cod, which 

 winters in the southwestern part of the Sea, also eats considerably less. After 

 intensive spring feeding the cod may pass through a period of compulsory 

 starvation, when the pelagic fish (herring and caplin) migrate from the regions 

 where cod dwell. 



