Effects of egg stocking density on survival, antioxidant defense status, and stress and immune responses in the first life stages of Binni (Mesopotamichthys sharpeyi)

Abstract

Binni (Mesopotamichthys sharpeyi) is a relatively new cultured fish species and the hatchery phase protocols are still unsatisfactory. The objective of the present study was to examine the effects of egg stocking density on survival, antioxidant and health status of embryos, newly hatched larvae and exogenous-feeding larvae of Binni. The eggs were stocked at densities of 5000 (D5000), 7500 (D7500) and 9500 eggs/L (D9500) in flow-through incubators. Stocking densities above 5000 eggs/L resulted in significant reduction in survival but had no significant effect on water quality parameters. Glutathione peroxidase and superoxide dismutase activities were lower in embryos and exogenous-feeding larvae of the D5000 group than those of the D7500 and D9500 groups. Although catalase activity was significantly lower in embryos of the D5000 group, it was lower in newly hatched larvae and exogenous-feeding larvae of the D9500 and D7500 groups, respectively. Vitamin C was in higher concentrations in embryos and exogenous-feeding larvae of the D5000 group as compared to D7500 and D9500 groups. Lipid peroxidation was greater in embryos and newly hatched larvae under higher stocking conditions. Cortisol level was greater in embryos and newly hatched larvae of the D9500 group, but it was lower in exogenous-feeding larvae of the D9500 group. Lysozyme activity was lower in embryos and exogenous feeding larvae of the D9500 group, but it was not significantly different with that of the D7500 group. Based on the results of our study, the stocking density of 5000 eggs/L is recommended for Binni.