Toxicity of Un‐ionized Ammonia and High pH to Post‐larval and Juvenile Freshwater Shrimp Macrobrachium rosenbergii

Abstract

AbstractPost‐larval and juvenile Macrobrachium rosenbergii were exposed for 72 h at 29 C to four pH levels (8.5, 9.0, 9.5, 10.0) and four concentrations of un‐ionized ammonia‐nitrogen (0, 1, 2, and 3 mg/L NHj‐N). Results indicated potentiation between NH3 and high pH. Juveniles were more tolerant of high pH and NH3 than post‐larvae.For post‐larvae, estimates of 72 h LC50 for pH were 9.43, 9.21, and 8.71 at 0, 1, and 2 mg/L NH3‐N, respectively; 72 h LC50 estimates for NH3‐N were 2.18 and 1.45 mg/L at pH levels of 8.5 and 9.0, respectively. For juveniles, estimates of 72 h LC50 for pH were 9.91, 9.56, 9.04, and 8.76 at 0, 1, 2, and 3 mg/L NH3‐N, respectively; 72 h LC50 estimates for NH3‐N were 2.02 and 0.54 mg/L at pH 9.0 and 9.5, respectively.In pond culture of M. rosenbergii, high pH levels can cause mortality at stocking. The 72 h data can be used as an indication of safe stocking levels of pH and ammonia. These data suggest that post‐larvae should not be exposed to pH > 9.0 nor to NH3‐N > 1 mg/L in the pH range 8.5–9.0 and juveniles should not be exposed to pH > 9.5 nor to NH3‐N > 0 mg/L at pH 9.5, > 1 mg/L at pH 9.0, or > 2 mg/L at pH 8.5.