The results of a comparative analysis of some blood serum immune-biochemical indices of bream that inhabits lake Nero and the Rybinsk Reservoir are reported. The following indices were investigated: anti-microbial properties: proportion of immune-deficient animals, common lipids level and their fractional composition, content of malondialdehyde and antioxidant activity. Unlike fishes from relatively clean waters, fishes from ecologically unfavorable areas show low immune status, alterations in lipid metabolism and increased free radical oxidation.
