Serum haemolytic and agglutinating activity as indicators of fish immunocompetence: their suitability in stress and dietary studies

Gilthead sea bream, Sparus aurata, were subjected to different stressful situations and the haemolytic activity mediated by the alternative complement and the agglutinating serum activity were tested as indicators of immunocompetence. The results show that both parameters were significantly compromised after chronic or repeated acute stress as well as in groups fed with vitamin E or Ω3 highly unsaturated fatty acids (HUFA) deficient diets and in infected fish. These results suggest that both haemolytic and agglutinating activity are suitable indicators for immunocompetence as they are non-specific responses induced by non-specific stressors. In addition, a comparison is performed with other immune indicators subjected to the same stressors.