The fact that fish in the 5 ppt
treatment died in greater number compared to the other
treatments may be attributable to a lessened resistance to
disease or increased virulence of the parasite at a lower
salinity. Work with the gilthead seabream (Sparus
auratus) has shown that culture of these fish in low
salinities (6 ppt) can significantly decrease immune
responses such as peroxidase content and complement
activity compared to fish reared at higher salinities
(Cuesta et al., 2005).