For both doses of 1.0 108 and 1.0 109 CFU/fish, the RPSs at 15 and 30 days showed no significant difference (P > 0.05); compared to 1.0 108 and 1.0 109 CFU/fish doses, the RPSs of 1.0 106 and 1.0 107 CFU/fish dose groups dropped significantly (P < 0.01).