Fish blood parameters as a potential tool for identification of stress caused by environmental factors and chemical intoxication

Classical stress indicators (cortisol, glycemia, hemoglobin and hematocrit) and specific red blood cell responses of enzymes involved in protection against active oxygen species (superoxide dismutase (SOD), catalase and peroxidase activities) were investigated in sea bass (Dicentrarchus labrax) exposed to decreased salinity, increased temperature (physical stress) or to intoxication by metallic or organic compounds (chemical stress). Thermal stress led to a greater increase in glycemia, cortisol and peroxidase activity than osmotic shock, whereas SOD and catalase activities were more stimulated by osmotic shock. The most frequent responses of blood parameters to specific chemical intoxication involved peroxidase and MnSOD activities, and cortisolemia. Increased levels of cortisol were always found and were followed or not by enhanced glycemia. Pooling these results according to specific chemical families (metallic and organic compounds) revealed a low but general increase of total SOD activity in intoxicated fish. Some reference values were also given for each parameter, including possible variations related to sex, season or nutritional influences. The effect of fish catching, especially on glycemia and cortisolemia, was also evaluated.