Acute Toxicity of Ciprofloxacin, Norfloxacin and Florfenicol to Misgurnus anguillicaudatus

This study was conducted to investigate the acute toxic effects of ciprofloxacin, norfloxacin and florfenicol, which are widely used antibacterial drugs, on loach. Through a well-planned experimental design, we systematically monitored the physiological and behavioral characteristics of loach under different drug concentrations and exposure time, and evaluated the toxic effects of these drugs. Under specific test conditions, i.e. water temperature is maintained at (10.0 ± 2.0)℃, and the pH value was controlled in the range of 4.6 to 5.7. We tested the acute toxicity of the three drugs on loach with body length of (3.1 ± 0.2) cm and body weight of (1.8 ± 0.1) G. The results showed that the LC50 of ciprofloxacin hydrochloride, norfloxacin and florfenicol to Misgurnus anguillicaudatus were 169 mg/L, 276 mg/L and 452 mg/L in 24 hours, and 153 mg/L, 271 mg/L and 447 mg/L in 48 hours, respectively; The median lethal concentration at 72 hours and 96 hours also showed a corresponding trend. At the same time, we calculated that the safe concentrations of the three drugs to loach were 85 mg/L, 78 mg/L and 131 mg/L, respectively. By comprehensive comparison, the order of toxicity intensity of the three drugs to loach was as follows: ciprofloxacin hydrochloride ＞ norfloxacin ＞ florfenicol. This study not only provides a solid scientific basis for the rational use of drugs in aquaculture, but also contributes valuable data resources to the research in related fields, which has important academic value and practical significance.