The effects of water hardness on the hatching and viability of silver carp (Hypophthalmichthys molitrix) eggs

Abstract

An investigation was conducted to establish water hardness concentration for optimum hatching of silver carp (Hypophthalmichthys molitrix) eggs. Eggs were incubated for 19 h at 26.5°C at six levels of water hardness: 100, 200, 300, 400, 500 and 600 mg/l CaCO₃. Water absorption at 100–200 mg/l CaCO₃ caused eggs to burst prematurely and minimal water absorption occurred at 600 mg/l CaCO₃. Chloride concentration at 0 and 6 h post-fertilization was significantly related to egg hatchability. Total ammonia-nitrogen at 6 h, pH at 6 h, magnesium hardness at 18 h and chlorides at 18 h significantly influence viability of larvae. A water hardness of 300–500 mg/l CaCO₃ is recommended for the successful hatching of silver carp eggs.