Liver histopathology in roach (Rutilus rutilus) and bleak (Alburnus alburnus) from the Bolshoy Cheremshan river

The results of histopathological studies of the liver of two mass fish species of the Bolshoy Cheremshan River are presented: roach (Rutilus rutilus Linnaeus, 1758) and bleak (Alburnus alburnus Linnaeus, 1758). Using standard histological techniques, five types of detected liver disorders and pathologies were studied. The excess of normal indicators of the occurrence of fish with detected liver histopathologies in populations exposed to the greatest adverse effects was recorded, which is one of the signs of their distress in the environmental conditions of some sections of the watercourse. The number of individuals with liver histopathologies at two research stations reached high values, and the occurrence of detected types of pathologies exceeded the value of their spontaneous formation (1%). The revealed pathologies had different degrees of severity for fish (2-5 points on a five-point scale). On sections of the river with increased anthropogenic load, damage of an irreversible nature and life-threatening has been recorded. In areas of the river with increased anthropogenic load, damage of an irreversible nature and threatening the life of fish was recorded: dysplasia and lipoid degeneration of hepatocytes. Thus, the direct connection of the occurrence of the detected liver histopathologies with the level of anthropogenic load on the ecosystem of the studied reservoir has been confirmed. The possibility of using histological parameters of fish to assess the influence of a complex of unfavorable environmental factors on individuals as an indicator of the ecological state of the reservoir is shown. The presented data are the first data on the morphophysiological state of two fish species that form the basis of the ichthyofauna of the Bolshoy Cheremshan River.