A study of changes in some immunological parameters of fish blood serum depending on the average monthly air temperature was carried out. The studies were carried out on bream aged 3+, with an average weight of 375 ± 30 g and a length of 290 ± 20 cm, caught in the Volga reach of the Rybinsk reservoir. The fish were caught using fixed nets in February for several years and the average monthly air temperature was recorded. The studied fish were sampled from the tail vein. Blood was collected in a dry sterile test tube and kept at room temperature. After blood coagulation and retraction of the clot, the serum was taken with a syringe with a fine needle and transferred to another tube. To assess the state of natural immunity in the blood serum, the level of bactericidal activity and nonspecific immune complexes was analyzed. Based on the data obtained, the number of immunodeficient individuals was determined. Variations of the studied parameters in years different in average monthly air temperature were established. The greatest differences between the indicators were revealed in the years with the highest (2003) and lowest (2006) mean monthly temperatures. The minimum indicators of bactericidal activity were recorded in 2003, and the maximum — in 2006. The highest content of immune complexes and immunodeficient individuals was established in 2003, and the lowest in 2006. The study showed the relationship between an increase in the average monthly air temperature and a decrease in functional activity nonspecific humoral immunity. Based on the data obtained, it was concluded that the temperature factor influences the mechanisms of innate immunity of fish.

The results of a comparative analysis of some indices of humoral immunity and lipid metabolism sterlet Acipenser ruthenus, living in different parts of the Volga river. In the serum of the studied antimicrobial properties, the proportion of immunodeficient individuals, the content of nonspecific immune complexes, the level of total lipids and their qualitative composition. It is noted that sturgeon in the Lower Volga region in comparison with other populations has a higher immune status and the optimal ratio of lipid components.