Vaccination of Atlantic salmon ( Salmo salar L.) before and during smoltification; effects on smoltification and immunological protection

Abstract

The effect of vaccination of Atlantic salmon ( Salmo salar L.) at different times in relation to the smoltification process has been examined. Three groups of fish were vaccinated with an oil-adjuvanted vaccine, protective against Aeromonas salmonicida and Vibrio salmonicida: one group was vaccinated during smoltification, the other group close to smoltification, and the third group several weeks before smoltification. Different stages of smoltification were achieved by manipulation of the photoperiod and water temperature, and the process was followed biweekly by 24 h seawater challenge tests. Immunological protection against A. salmonicida and V. salmonicida was recorded after challenge with the live pathogens, and humoral immune response was measured by ELISA. The results showed that vaccination close to the start of smoltification disturbed the smoltification process and caused a delay of approximately two weeks. Vaccination at this time, however, yielded high immunological protection and humoral immune responses, indistinguishable from those obtained in fish vaccinated several weeks before or during smoltification.