TOLERANCE OF SNAKEHEAD CHANNA-STRIATUS TO AMMONIA AT DIFFERENT PH

Tolerance of snakehead Channa striatus to ammonia was tested at three pH levels (8.0, 9.0, and 10.0) in experimental tanks. At pH 8.0, ammon ia LC50 estimates for snakehead at 24, 48, 72, and 96 h were >205.7, > 203.5, 152.6, and 107.3 mg total ammonia-nitrogen (TAN)/L (or >10.3, > 10.2, 7.6, and 5.4 mg NH3-N/L), respectively. At pH 9.0, ammonia LC50 estimates at 24, 48, 72, and 96 h were >52.4, 62.8, 56.1, 43.4 mg TAN/ L (or >18.0, 21.6, 19.3, and 14.9 mg NH3-N/L), respectively. At pH 10. 0, ammonia LC50 estimates at 24, 48, 72, and 96 h were 25.7, 21.6, 20. 3, and 18.7 mg TAN/L (or 21.6, 18.1, 17.1, and 15.7 mg NH3-N/L), respe ctively. Our data indicate that the tolerance of snakehead to ammonia was associated with pH. Thus, we recommend that snakehead should not b e subjected to prolonged exposures of NH3-N concentration more than 0. 54 mg/L at pH 8.0, more than 1.49 mg/L at pH 9.0, or more than 1.57 mg /L at pH 10.0.