The Effect of Sudden Rise in Salinity on Survival Rates and Salinity Tolerance Ability of Ctenopharyngodon idella

This study aimed to identify the extent of the effect of sudden rise in salinity on survival rates of Ctenopharyngodon idella and determine the lethal concentration (LC50) that kills half of the number of fish. The fish were suddenly exposed to lethal concentrations (LC50 values) of: 4, 8, 12, and 16 g / l at a weight of 31.4 ± 2.2 g, as well as hypertonic water at the rate of (0.1 g of LC50), which was considered as a controlling sample. The (LC50) were prepared by adding a known weight of dried sea salt in a liter of chlorine-free hypertonic water until the required lethal concentrations (LC50) were reached. The results of the survival rates experiment showed that the survival rate of Ctenopharyngodon idella reached 90%, 20% and 0% at the lethal concentration (LC50) of 8, 12 and 16 g /I respectively, while the survival rate was 100% in both hypertonic water and the lethal concentration (LC50) of 4 g / l.

The results of the experiment to determine the lethal concentration (LC50) that kills half of the number of fish also showed that the LC50 in Ctenopharyngodon idella reached 9.68 g / l during 96 hours of sudden exposure to LC50 at the rate of 0.1, 4, 8, 12 and 16 g / l. During the experiment, the fish were fed on food ration containing 32% protein, at the rafe of 3% of the weight of fishs' body.