Abstract
Thiamethoxam (TMX) is a highly toxic systemic neonicotinoid pesticide and its entry into water bodies can greatly endanger human health and aquatic ecosystems. Little is known about the effect of thiamethoxam on Nile Tilapia. Particularly so this experiment was scheduled for three weeks to evaluate the toxic effects of thiamethoxam on productive performance of fish as well as water quality. The used insecticide was Actara 25 WG manufactured by Sygenta, Egypt and it was purchased from Egyptian Company for Seeds and Agricultural Chemicals. It composed of 250 g/kg Thiamethoxam. A total of 200 Oreochromis niloticus with an average initial weight of 15 ± 5 g have been obtained from a commercial fish farm in Kafr Elsheikh province, Egypt. Fish were randomly allotted to five replicated treatments and they were kept at a density of 10 fish / aquaria. Four different concentrations of the insecticide were tested with three replicates of fish for each treatment beside a control group where with no insecticide were used. Tested concentrations of studied insecticide was selected according to lethal concentration 50 (LC50) for Thiamethoxam was 500 mg/l. Statistical analysis of the recorded data clarified that the levels of pH, dissolved oxygen levels (DO), oxygen saturation percentage (DO%) and salinity were significantly different between thiamethoxam treated groups and the control group. In addition, there was a significant difference in final weight and weight gain of fish under experiment in all treatments when compared with the control group. In addition, the lowest significance in the final weight and weight gain was observed at the high chronic dose. Finally, there were no significant differences in mortalities between various treatment groups and the control group with exception to high subacute dose that showed the highest significance of all groups and it was clear that mortalities were increased with increasing thiamethoxam dose as no mortalities were observed in the control group. The present trial clearly showed the toxic effects of thiamethoxam on water quality of fish tank as well as performance and mortality rate in Nile tilapia fish that were live for three weeks in polluted water. Moreover, the result of the present study is of great public health importance because of thiamethoxam residue effects on human health.

Key words: Thiamethoxam, Nile tilapia, productive performance, water quality