ASSOCIATION BETWEEN IMMUNIZATION, REDUCED WEIGHT-GAIN AND PLASMA-CORTISOL CONCENTRATIONS IN JUVENILE BALTIC SALMON (SALMO-SALAR)

The changes in plasma cortisol levels, immune response parameters and growth of juvenile Atlantic salmon (Salmo salar) were monitored during a 50 days period following a DNP-HSA (di-nitrophenyl human serum albu min) immunisation program. Antibody titers rose significantly after a single immunisation. An increased plasma cortisol concentration was ob served in association with injection of both antigen and saline. A sin gle injection had a significant negative effect on growth of fish and fish subjected to 2 injections with a 25 days interval had an even lar ger growth reduction. The plasma cortisol concentration and the specif ic antibody response were compared at an individual level but no corre lation was found. Total serum protein increased during the experimenta l period independently of immunisation. In contrast the total serum im munoglobulin 50 days after the first immunisation was clearly connecte d to antigen exposure. The observations are discussed in relation to i mmunophysiological changes during immunisation and stress induction.