670 



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



The composition of food for the fish, which also inhabit the open parts of 

 the Sea, changes considerably near the shores, where gammarids become 

 less and molluscs more significant; Ostracoda is added to the diet. Some 

 shorter food chains make their appearance (for example: phytobenthos — 

 rudd — pike perch) ; plankton is even less important. 



V. Pankratova (1935) has shown that fish feed more on vegetable food in 

 the winter than in the summer, and more on animal food in the summer than 

 in the winter. According to this worker (Fig. 318) Acipenser nudiventris feeds 

 exclusively on molluscs. The diets of vobla (Rutilus rutilus aralensis) and 



2 3 4 



Molluscs 



Gammaridae 

 E2 Phryganidae 



8 



t^i High crustaceans 

 P??H Vaucheria 



I — | Diaptomus 

 sal in us 



10 



ШВ Chironomidae 

 Fig. 318. Food composition for Aral Sea fish (Pankratova). 1 Acipenser nudiventris; 

 2 Rutilus rutilus ; 3 Barbus brachicephalus ; 4 Chalcalburnus chalcoides ; 5 Abramis 

 brama; 6 Abramis sapa; 7 Pelecus cultratus; 8 Cyprinus carpio; 9 Perca fluviatilis; 



10 Pungitius platygaster. 



bream {Abramis sapa) are the most varied, and the ratio of their components 

 is very similar. Vegetable food is most significant in both diets: for vobla 

 63-5 per cent of fish had some remains of vegetable food in their intestines, 

 and 49-5 per cent of them had only vegetable food in their intestines. Among 

 the animals molluscs and insect larvae are predominant in the vobla's diet. 

 Forty per cent of bream {Abramis sapa) had vegetable food (Vaucheria, and 

 other filamentous algae), and among the animals caddis and beach fleas are 

 predominant. 



Barbus brachycephalus feeds mostly on molluscs, and to a much smaller 

 extent on gammarids and higher plants. 



Chalcalburnus chalcoides aralensis feeds on gammarids and phriganids, and 

 Abramis brama eats all the benthos, but mostly gammarids and chironomid 

 larvae. Pelecus cultratus preys almost exclusively on animals and mainly on 

 beach fleas. It swallows also a number of land insects which fall into the water. 



The main diet of Cyprinus carpio is chironomid larvae, and to a lesser extent 



