Determination of AquaStart median lethal dose (LC50) as a disinfectant agent and study of the gill pathological effects on fry rainbow trout (Oncorhynchus mykiss)

Aquastart is introduced as a peroxide-based disinfectant agent in aquaculture industries of Iran for the first time. This study was designed to determine the median lethal dose (LC50) for 96 hours and histopathological finding in gill tissue. On fry rainbow trout. The research was carried out by 510 rainbow trout fry with an average weight of 1.33±0.01 grin 30 liter tanks under static conditions. Fish was exposed to 65, 75, 80, 85, 95, 100, 110 and 115 ppm concentrations of Aquastart for 96 hours. LC50 value of 89.4 mg/L was estimated for Aquastart by collecting the mortality of fish during 96 hours with using of probity analysis. It was found that in the lethal concentrations of Aquastart abnormal symptoms such as open-mouthed swimming, flashing, gasping for air, sinking to the bottom, balance gone, turned upside down and open-mouthed death were observed in comparison to control group. The histological investigation showed a range of histopathological alternations in gills tissue including epithelial cells necrosis, hyperplasia, hyperemia, lamellar adhesion and clubbing of at the tip of secondary gill lamellae. However, the severity of these alternations increased with increasing of the doses of Aquastart and extensive necrosis was observed in this regard. The highest mortality rate was obtained with increasing duration of exposure and concentration of Aquastart, according to increased toxicity of the agent. This study will be the basis of in vivo research for this disinfectant agent.