NNV-specific antibody responses of sea bass juveniles. RBS or CHV were used as vaccines in high concentration (V.H. or H.H.) and low concentration (V.L. or H.L.) to intramuscularly vaccinate sea bass juveniles, and PBS were used as the negative control. In each group, sera from 30 randomly selected fish were collected every week post-immunization for antigen-capture ELISA to monitor the antibody titers. NNV-specific antibody responses of sea bass juveniles stimulated by RBS or CHV with one (A) or two (B) injections are shown. The letters (a, b, and c) indicate the differentiation analysis results of each sample using the Student’s t test. The samples with the same letter contained no significant difference (p > 0.05) while the samples with different letters held significant difference (p < 0.05).