Study of development of antioxidant defense in early life stages of Oncorhynchus mykiss

In aquaculture egg incubation is a most critical time as fish are vulnerable to environmental factors, so characterization of antioxidant enzymes development in this stage of life is a great scope of recently researches. Stocking density induced stress that affects energy intake, growth rate, enzymatic activity and oxygen consumption in fish. In this study the development of some antioxidant enzyme (GPX, CAT and SOD) in serum of rainbow trout (Oncorhynchus mykiss) that kept in different stocking density was investigated. Lipid peroxidation and serum concentration of MDA evaluated as well. Eggs were held in tanks supplied with flow-through freshwater at 10.8̊C in triplicate. Samples were taken at day1 (fertilization), 3 (Cleavage), 8(organogenesis), 16 (eyed egg), 31 (hatch) and 48 (active feeding). A significant increase in GPX and SOD activity was seen from fertilization till eggs were eyed. (P<0.001).Activity of these enzymes decreased to active feeding (P<0.001), meanwhile the activity was higher than fertilization. Our results demonstrated that catalase activity increases from fertilization to organogenesis and then toward active feeding significantly decreased in compare to fertilization (P<0.001). Overall trend of MDA concentration showed significant increases from fertilization toward active feeding in all groups (P<0.001).