EFFECT OF AN ABRUPT TRANSFER TO DIFFERENT SALINITIES ON ABILITY OF SALT TOLERANCE IN GOLDFISH CARASSIUS AURATUS

Abstract

This study carried out to investigate the effect of an abrupt increasing of salinity on survival rates and defining the Lethal concentration (LC50) which kills 50% of goldfish Carassius auratus. Fish at average weight 39.5 ± 2.5 g were exposed to different salt concentrations: 0.1, 4, 8, 12 and 16 g/l, where each concentration represented a treatment, while the first treatment represented as a control. The results showed that the survival rates of goldfish were 100% in 0.1, 4 and 8 g/l, while it was 40% and 0% in 12 and 16 g/l salt concentrations, respectively. The LC50 which killed 50% of goldfish was 10.96 g/l during 96 hours of an abrupt exposure to salt concentrations: 4, 8, 12 and 16 g/l. Fish were fed a diet contained 32% protein at a ratio 3% of fish body weight.