Hatchability of eggs from Atlantic cod, turbot and Atlantic halibut after disinfection with ozonated seawater

In aquaculture the risk of transmission of fish pathogens via eggs is reduced by disinfection in ozonated seawater, but this treatment may delay or reduce hatching. The objective of this study was to investigate the tolerance of Atlantic cod, turbot and Atlantic halibut eggs to ozonated seawater. Groups of eggs were treated with different concentrations and exposure times 2 days before hatching, and the effects on hatchability were observed. The groups of eggs of all three species that had been exposed to 2 mg O-3/l for 2 min or less showed normal hatching. In the groups with high total exposure (4 mg O-3/l for 1 min or higher), a clearly lower percentage of hatching was found. Interspecies differences in tolerance were observed, with turbot eggs displaying higher tolerance than eggs of either halibut or cod. Due to the interspecies differences, the tolerance of eggs to ozonated seawater should be carefully evaluated in controlled laboratory-scale experiments in order to establish a basis for disinfection protocols. Two milligrams O-3 per liter for 2 min and lower exposures ought to be sufficient to ensure an excess of oxidants for efficient inactivation of fish pathogens while avoiding negative effects on the hatchability of halibut, cod and turbot eggs. (C) 2003 Elsevier Science B.V. All rights reserved.