Serum protein and IgM profiles in connection with the smolting and vaccination of out-of-season Atlantic salmon ( Salmo salar L.)

Abstract

The concentrations of serum proteins and IgM were measured in vaccinated and untreated out-of-season smolts. Out-of-season (0+) smolts were produced by exposing parr to continuous light (LD 24:0) until June 5 followed by a “winter” photoperiod of LD 12:12 for 6 weeks, and then continuous photoperiod (LD 24:0). The fish were vaccinated in the “winter” photoperiod using a commercially available quattro vaccine. The IgM levels remained low throughout the “winter” photoperiod, and increasing IgM levels were observed from the time of introducing the continuous photoperiod. The serum protein levels decreased at the start of the “winter” photoperiod, and increased at the beginning of the subsequent exposure to LD 24:0, but after 2 weeks the levels dropped again and remained low for the further 2 weeks before sea water transfer. For 1+ smolt, a synchronous drop in both serum proteins and IgM during smolting have been shown, indicating that 1+ and out-of-season smolt are not always comparable. Both serum IgM and protein concentrations increased after vaccination with an oil adjuvant quattro vaccine. The increase in serum proteins exceeded that of IgM. The sea water adaptability of the out-of-season smolt was affected by the vaccination as shown by an transient increase in serum chloride levels. Vaccination with oil adjuvant vaccines close to sea water transfer may therefore interfere with or delay the smolting process.