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



Characteristically, mackerel feeds intensively during the period of its 

 spawning migration. After spawning, mackerel concentrates in the northern 

 part of the Sea in large numbers for feeding. It feeds mostly on large copepods 

 {Calanus tonsus, C. finmarchicus) and euphausiids (Thysanoessa raschii and 

 77?. sp.) and, as a predator, consumes also fish fry. 



The study of the feeding habits of flatfish (Pleuronectidae family) of the 

 Far Eastern Seas (N. Gordeev, 1954; L. Mikulich, 1954) has shown that 

 halibut {Hippoglossus hippoglossus stenolepis, Reinhardtius hippoglossoides 

 matsurae, Atherestes evermanni) lives mostly on fish. Seventy-two per cent of 

 the diet of the first-named consists of fish (pollack, sand-eel and others). The 



Fig. 385. Food correlation of plaice in the area of the southeastern coast of 

 Sakhalin (Mikulich, 1954). Thick lines — strong food correlations ; thin lines — 

 average, broken lines — weak food correlations. 1 Limanda aspera ; 2 Platessa 

 quadrituberculata ; 3 Pleuronectes stellatus ; 4 Limanda punctatissima probos- 

 cidea ; 5 L. p. punctatissima ; 6 Glyptocephalus stelleri ; 7 Pseudopleuronectes 

 yokohamae ; 8 Acanthopsetta nadeshnyi ; 9 Hippoglossoides elassodon dubius ; 

 10 Atheresthes evermanni; 11 Hippoglossus hippoglossus stenolepis. 



second place in its diet is occupied by large crustaceans (crabs, hermit crabs, 

 amphipods, prawns) and large molluscs (Seripes groenlandicus and cephalo- 

 pods). 



The majority of the Pacific Ocean flatfish, in contrast to halibut, are bentho- 

 pages (worms, polychaetes, molluscs, sometimes bottom-living crustaceans 

 and echinoderms). The diet of some flatfish is mixed, both fish and pelagic 

 crustaceans forming at times a considerable part of it (Figs. 385 and 386). 

 Stomach repletion indices of halibut and flatfish are 150 to 200, rising some- 

 times to 300 or even 600. The nature of the food of the Far Eastern Pleuro- 

 nectidae, both halibut and flat flounder, is very similar to that of those in the 

 Atlantic. 



Owing to the peculiar temperature conditions of the surface water and the 

 narrowness of the shelf zone, the migrations of Pleuronectidae in the Sea of 

 Japan have a destructive character, similar to that of cod and Kamchatka 

 crab (Fig. 387). In summer they feed intensively in the off-shore areas which 



