THE ARAL SEA 671 



molluscs, pelagic crustaceans and plants. Perca fluviatilis feeds exclusively 

 on gammarus, and Pungitius platygaster aralensis is a typical planktophague. 

 Its main food is Diaptomus salimts, and a supplementary one is chironomid 

 pupae. Silirus glanis, Lucioperca lucioperca, Aspius aspius illiodes and Esox 

 lucius are predators which feed on fish and very rarely eat other animals and 

 plants. 



Acclimatization measures. In recent years acclimatization measures in the 

 Aral Sea have acquired a systematic character. In this work the high food 

 value of the benthos, in spite of its small biomass, is taken into consideration 

 as well as the great poverty of plankton food and the presence of considerable 

 amounts of mostly vegetable organic detritus. 



Adult Acipenser stellatus was brought from the Caspian Sea in 1933-34. 

 Acclimatization measures were again undertaken in 1948-56. Acipenser stella- 

 tus, however, was brought as roe from the delta of the Ural river. Both species 

 of grey mullet (Mugil auratus and M. saliens) and with them both species of 

 prawns {Leander adspersus and L. squilla) were also brought from the Caspian 

 Sea into the Aral Sea in 1954-56, while during the same years the roe of 

 Clupea harengus membras came from the Baltic Sea. The transplantation of 

 Baltic herring and its successful development in the Aral Sea is of special 

 interest, the more so since in its new habitat the fish grows quicker and larger 

 in size (two or three times larger). The severe temperature conditions of the 

 Aral Sea might cause some doubts about the acclimatization of grey mullet ; 

 but as a mud-eater it has plenty of food there. So far it has not been discovered 

 in the Aral Sea. 



Two species of Caspian bullheads {Pomatoschistus caucasicus, and Gobius 

 melanostomus affinis) and three species of Caspian mysids {Mesomysis kowa- 

 lewskyi, Mesomysis intermedia and Par amy sis baeri) were brought into the 

 Aral Sea with the grey mullet (1958). 



The fish Atherina mochon pontica caspia was brought in by accident. A 

 future possibility is the transplantation into the Aral Sea of forms successfully 

 acclimatized in the Caspian Sea — Nereis and Syndesmya and others. The 

 success of the transplantation of the Baltic herring into the Aral Sea is an 

 indication that other inhabitants of the Baltic might later be transplanted too. 

 Among the invertebrates the bivalve Macoma baltica seems to offer some 

 possibility of acclimatization in the Aral Sea. 



Fishery. Carp, bream and vobla are the main items of commercial fishery in 

 the Aral Sea. Chalcalburnus, catfish, Abramis sapa, barbel pike, pike perch 

 and Aspius aspius are of less importance. The total catch in recent years 

 (1956) has reached 459 centners. In 1956 there was a total yield of 166,000 

 centners of bream, 100,000 centners of carp, 57,000 centners of vobla, 25,000 

 centners of pike, 23,000 centners of Chalcalburnus, and 9,000 centners of 

 pike perch. Fishing has so far been done mainly in the in-shore areas, chiefly 

 in the mouths of rivers. 



