Within the project “Development of evidence-based recommendations for increasing the fish productivity of fishery reservoirs through the introduction and reintroduction of fish and hydrobionts – components of the food base of fish” of the program «Complete assessment of the state of fish resources and other hydrobionts of the main fishing water reservoirs of Kazakhstan and the development of evidence-based recommendations for their sustainable use» works on testing the survival of the polychaete Hediste divesicolor (O.F. Müller, 1776) of the Aral Sea in natural water with different mineralization is continue by the efforts of the employees of the laboratory of hydrobiology and hydroanalysts of the head unit of “RPC of Fisheries” LLP. During the experiment, observations are also made of the feeding behavior and dietary preferences of polychaetes.