Level of oxidative processes and total lipids in immunocompetent organs of bream of the Cheboksary reservoir

The Cheboksary Reservoir is located in the Middle Volga basin. Its ichthyofauna comprises 50 fish species belonging to 16 families. Of the majority of reservoir fish species, the bream Abramis brama (Linnaeus, 1758) is the most commercially important. This study examines selected biochemical parameters of bream from different parts of the Cheboksary Reservoir. The fish were caught using a bottom trawl during a comprehensive hydrobiological expedition. After necropsy, kidney, spleen, and liver samples were collected in sterile test tubes. Homogenates were prepared from the organ tissues using a homogenizer with 0.65% saline at a weight-to-volume ratio of 1:6 and 1:1. The homogenates were analyzed for lipid peroxidation, antioxidant defense, and total lipids. The liver and kidneys of fish showed higher levels of the studied parameters compared to the spleen. High levels of peroxidation and total lipids were observed in fish inhabiting the upper reaches of the reservoir, while antioxidant defense was higher in fish from the lower reaches. Differences in the intensity of oxidative processes are likely due to different levels of antioxidant enzymes. High total lipid concentrations in the organs of bream from the lower reaches indicate favorable feeding conditions. These differences are likely related to the impact of various environmental factors on the fish, water quality, and the level of food supply in the studied areas of the Cheboksary Reservoir.