Abstract:

During keep-alive transportation of aquatic products, higher-level molecular ammonia and nitrite were often accumulated in water. In order to explore the safe concentration of molecular ammonia and nitrite in water for adult Siniperca chuatsi, an acute toxicity test was conducted to examine the effect of molecular ammonia and nitrite on adult Siniperca chuatsi under the environment of 18－20 ℃ for water temperature, 3‰－4‰ of salinity, pH 7.31－7.57, and 8.2－8.5 mg/L of dissolved oxygen (DO). Results indicated that median lethal concentrations (LC50) of molecular ammonia were 0.389, 0.295 mg/L and 0.193 mg/L at the time point of 24, 48h and 96 h, respectively. Thus, the safe concentration of molecular ammonia in water for Siniperca chuatsi was 0.0193 mg/L. Similarly, median lethal concentration (LC50) of nitrite were determined to be 196.32, 91.69mg/L and 75.4 mg/L so that its safe concentration was 7.54 mg/L. Based on above investigations, molecular ammonia in water exhibited obvious toxicity to adult Siniperca chuatsi, and resulted in the death of fish although adult Siniperca chuatsi revealed resistance to nitrite toxicity to some extent. Therefore, quality monitoring of water to control the contents of ammonia, nitrogen and nitrite during keep-alive transportation of aquatic products is an effective strategy to improve the survival rate of fish.

Key words: molecular ammonia, nitrite, adult Siniperca chuatsi, toxicity, median lethal concentration