Study on Acute Toxicity of Trichlorfon and Formaldehyde to the Larva of Carassius auratus in Qihe River

[Objective] The research aimed to study acute toxicity of drugs to the larva of Carassius auratus in Qihe River.[Method] Under the indoor normal temperature and hydrostatic conditions,with larva of Qihe Carassius auratus as the test organism and lethal rate as the index,acute toxicity of formaldehyde and trichlorfon to the larva was studied.[Result] Within the same exposure time,the higher the concentration of formaldehyde and trichlorfon solution,the more the mortality of larva.Semi-lethal concentration(LC50) of trichlorfon at 24,48 and 96 h were 108.63,89.20 and 75.30 mg/L,its safe concentration(SC) was 7.53 mg/L;while semi-lethal concentration(LC50) of formaldehyde at 24,48 and 96 h were 165.33,134.04 and 119.42 mg/L,its safe concentration(SC) was 11.94 mg/L.[Conclusion] In the disease prevention of Qihe Carassius auratus larva,trichlorfon is safer and formaldehyde should be used with caution.