The imunnocompetent cell population size including lymphocyte, neutrophil and eosinophil populations, lysozyme activity in plasma and the growth performance were assessed in great sturgeon Huso huso after oral administration of Ergosan at 0.5% of the feed and Vitacel at 1.3% of the feed for 90 days. Sampling was performed on 15 and 90 days during feeding trial. Generally, a significant increase was seen in the lymphocyte count of fish received Ergosan compared to both Vitacel and control groups 90 days post-treatment (P<0.05). Interstingly, at the Neutrophil profile of fish fed Vitacel and VitacelErgosan combination was observed significant increase on 90 days after trial (P<0.05). The number of eosinophils tended to be higher in Vitacel group (P<0.05) on day 90 and was significantly higher (P<0.05) than in Ergosan and control. Also, lysozyme activity in plasma of treatment fish by Ergosan and Vitacel was significantly higher than control group on 15 and 90 days post-treatment (P<0.05). In addition, the weight of fish fed diet containing Ergosan and/or Vitacel had a significant increase compared to control group on days 15 and 90 of trial (P<0.05).Keywords: Ergosan, Vitacel, Huso huso, Lysozyme, Growth performance. Gelişkin Mersin Balıklarının (Huso