Determination of sub-lethal concentration of ammonia (LC50 96h, N-NH4) in Acipenser persicus and Huso huso, invitro

The experiments were done to determination of LC50 of ammonia (N-NH4, 96h) to Acipenser persicus and Huso huso. 12 A. persicus and 15 H. huso with average weight of 46±5g were exposed to different concentrations of ammonia salt. A group of fishes considered as control. The experiments were done by static method during 96h. Under of stable condition of temperature and pH, the lethal concentrations of ionized ammonia were 35 and 50mg/l for A. persicus and H. huso, respectively. The LC50 (median lethal concentration) were 18.65 and 29.22mg/l N-NH4 for A. persicus and H. huso, respectively by used of linear regression of mortality percentage to ammonia different concentrations. Results showed that there was significant differences between treatment and control group (P<0.05). Histopathological findings of gills showed that major lesion were hermorrhage, hyperemia, hyperplasia and edem. The results revealed, necrosis of gills were less for Acipenser persicus and Huso huso.