Current state of juvenile roach (Rutilus rutilus caspicus)

Abstract

Fluctuations in water temperature in the Northern Caspian Sea, especially in the shallow zone, are mainly due to fluctuations in air temperature and during the trawling period, in the fall, the water temperature at observation stations showed a decrease in water temperature, which caused the formation of dense aggregations in juvenile roach. To study the nutritional status of juvenile fish living in the Kazakh part of the Caspian Sea, material was selected from different depths of the sea from trawl catches during comprehensive research in the fall of 2022. In the course of studies conducted to assess nutrition using quantitative and qualitative indicators, it was determined that the nutritional spectrum of juvenile roach in the water Caspian Sea is represented mainly by the same bottom organisms with a dominance of crustaceans, with their preference for bivalves, which give a good growth rate. A parasitological study of juvenile roach showed the absence of pathogen circulation in the ecosystem of this reservoir. Based on the results of pathomorphological studies of fish gills, it was found that fragmentary hyperplasia is caused by the presence of protozoal invasion rather than by the influence of environmental factors.