C3 and infection: Before infection, hepatic lysozyme and complement C3 (Figure 3F) contents in fish in 0.5–2‰ treatments were significantly higher than those in fish in control, 4 and 8‰ treatments (Figures 3G,H); with extended infection time, the lysozyme content in fish in 2 and 4‰ treatments were significantly higher than in fish in other treatments at 48 hpi.