Water hardness does not influence iodine-induced mortality of rainbow trout eyed eggs

To evaluate the effects of water hardness on survival to hatch of eyed rainbow trout Oncorhynchus mykiss eggs during iodophor disinfection, hard (300 mg/L CaCl2) and soft water (20 mg/L CaCl2) solutions were used in combination with iodophor treatments of 0, 100, 200, 400, 800, and 1600 mg/L. Water hardness did not significantly influence egg survival-to-hatch. In addition, there was no significant interaction between water hardness and iodine concentration on egg survival. However, significant differences in egg survival due to iodine concentration were observed. Egg survival significantly decreased at 800 mg/L, with near complete mortality occurring at 1,600 mg/L. Rainbow trout eyed egg disinfection using iodine concentrations of 800 mg/L or greater are not recommended, regardless of water hardness (calcium) concentrations. Keywords: Eyed eggs, iodophor, disinfection, rainbow trout, water hardness, mortality.