A higher infestation with S. chrysophrii was already established in Evoikos gulf cages at the commence of experimentation (Table 4). Prevalence was 100% in both groups and mean intensity reached values up to 17 adults with however no statistical differences among treatments. Both parameters remained at the same high level in samplings carried out in 30 and 60 d following initiation of therapy. F. echeneis was rarely seen at the end of the trial and monogenean eggs in general were absent. Growth and mean intensity between the experimental groups were not significantly affected by caprylic acid treatment during the 2-month medication period. Part of sampled fish appeared to be anaemic and emaciated but cumulative mortalities were however not considerable, reaching values as low as 0.4 and 0.6% in treated and control fish, respectively.