Using galvanized materials to control Cryptocaryon irritans infestation

Abstract

Infection by Cryptocaryon irritans, a ciliated protozoa parasite of marine fish, causes mass mortality and economic loss to the mariculture industry. In this study, plate and mesh galvanized zinc were embedded on the bottom of seawater to evaluate the protection to susceptible host Trachinotus ovatus from C. irritans reinfection at various seawater exchange rates and dosages. Furthermore, an evaluation of the zinc ion released from galvanized materials was carried out through detection of the zinc ion content in seawater and muscle tissue, and the observed pathological changes of liver. The results showed that, at all flow exchange rates (0, 50, or 1200%), the parasite abundance of infected T. ovatus were significantly decreased with galvanized materials. Survival rates were 100% at 14 days post infection when 56.25% of the tank was covered with galvanized iron plates or galvanized iron mesh at a dose of 0.2 m2/m3. The zinc ion concentrations in seawater after using galvanized materials increased continuously. However, residual zinc ion in the muscle of T. ovatus were not significantly different to the control group. Furthermore, no obvious pathological change was observed in the liver of T. ovatus. Consequently, using galvanized materials can control the reinfection of C. irritans and poses no threat to protected fish. Therefore, the use of galvanized materials could be a promising strategy to control cryptocaryoniasis.