Short time exposure to lethal concentrations of unionized ammonia in common carp (Cyprinus carpio) fingerling

In this study the effects of high levels of ammonia on behavioral changes and determining of lethal dose (LC50) were examined in common carp. In this regard, 180 Common carp (Cyprinus carpio) fingerling with average weight of 3.1±0.4 g divided in 18 aquaria with a density of 10 fish (per tank) for 2 weeks (for adaptation to the environment), in this study 5 treatment and a control groups with three replicates were considered. Treatment groups were exposed to total ammonia at concentrations of 1.25, 2.5, 3.75, and 6.25 m/l respectively that were equal to 0.34, 0.66, 0.99, 1.32 and 1.65 m/l of unionized ammonia. According to the results, unionized ammonia 96 h median lethal concentration calculated as 1.17 m/l for common carp. Nervous and unbalanced swimming was the most behavioral sign in fish that exposed with 1.65 m/l of NH3, first mortality observed 16 hours post exposure in this group. In fish of treatment 4 and 5 (exposed with 0.34 and 0.66 mg/l of NH3) slow swimming, lethargy and bottom sitting were the most clinical signs after 24 h exposure but no mortality was observed in these groups during experiment. According to the results of this study maximumm sub-lethal concentration of NH3 for common carp calculated as 0.12 mg/l.