CAT and infection: After 96 h of infection, the red blood cells, hemoglobin, hematocrit, and white blood cells of fish in 1‰ APS treatment were significantly lower than those of fish in 4 and 8‰ treatments; hepatic catalase activity was activated at 48 h, superoxide dismutase activity was also significantly upregulated at 96 h, and the malondialdehyde content significantly decreased.