Effects of pH on survival, growth, molting and feeding of giant freshwater prawn Macrobrachium rosenbergii

Abstract

The 24-, 48-, 72- and 96-h LC50s (median lethal concentrations) of pH on Macrobrachium rosenbergii juveniles (0.13 +/- 0.01 g) were 4.00, 4.05, 4.07 and 4.08, respectively. Survival rates of M. rosenbergii juveniles (2.65 +/- 0.06 g) following 56 days exposure to pH 8.2, 7.4, 6.8, 6.2 and 5.6 were 100%, 88.9%, 94.4%, 94.4% and 94.4%, respectively. After 42 days of exposure, the body weight and total length of prawns placed in pH 5.6 were significantly lower (p<0.05) than those placed in pH 8.2. The 42- and 56-day EC50s of pH (pH level that reduced weight gain by 50% of that of the controls) were pH 5.61 and 6.25, respectively. After 56 days of exposure, M. rosenbergii juveniles placed in pH 6.8 exhibited significantly lower molting frequency and body weight gain. Feeding rate was reduced in M. rosenbergii juveniles (2.06 +/- 0.10 g) exposed to pH 6.8 and lower. The minimum acceptable pH levels were 6.2 and 7.4 based on growth and feeding, respectively. (C) 2003 Elsevier Science B.V. All rights reserved.