Relationship between mean monthly February temperature and the level of oxidative processes in immunocompetent organs of bream of Rybinsk reservoir in different years

The intensity of oxidative processes in immunocompetent organs of immature bream Abramis brama L. with an average weight of 375±30 g and length of 290±20 cm was studied. The fish were caught with shuttle nets in the Volga Plec of the Rybinsk reservoir in different years in terms of average daily temperature conditions. After autopsy, samples of immunocompetent organs (kidney, spleen and liver) were taken from captured fish into sterile tubes. Samples were then frozen and stored in a freezer at minus 18–20 °C until processing time. In laboratory conditions, samples were thawed at room temperature immediately before analysis. For further studies, homogenate was prepared from kidney, spleen and liver tissues using a homogenizer with physiological solution in the ratio of 1:1. In the homogenates the content of lipid peroxidation products was studied by the content of malonic dialdehyde and the level of antioxidant defense by the index of inhibition of substrate oxidation. The interannual variability of the studied parameters was noted, associated with ecological and climatic conditions, in particular, with temperature. The most significant differences of the studied biochemical parameters were revealed in the year with the highest temperature conditions compared to the year with the lowest temperature. The lowest values of malonic dialdehyde and substrate oxidation constant were observed in fish in the year with the lowest average daily temperature. In warmer year intensification of lipid peroxidation processes and decrease of antioxidant defense level in the studied organs were observed. The results obtained can be used in monitoring the impact of climatic factors on the physiological and biochemical status of fish.