TOXICITY OF AMMONIA TO FINGERLING WHITE BASS - EFFECT OF SELECTED ENVIRONMENTS ON UPTAKE DYNAMICS

The 96-h median lethal concentration of un-ionized ammonia-nitrogen fo r fingerling white bass Morone chrysops (mean weight +/- SD, 4.4 +/- 1 .42 g) at 19.7 +/- 0.4 degrees C was 0.63 +/- 0.17 mg/L in soft (less than or equal to 5.0 mg calcium/L) freshwater. The uptake of ammonia b y fingerling white bass (mean weight, 14.0 +/- 2.74 g) was similar in soft freshwater, hard (78.3 +/- 3.80 mg calcium/L) freshwater, and dil ute (7.4 +/- 0.30 g sea salt/L) seawater. However, exposure time did a ffect the concentration of plasma ammonia in exposed white bass. Based on the observations in this study and others, it is estimated that gr owth of fingerling white bass should not be inhibited if fish are cont inuously exposed to un-ionized ammonia nitrogen at 0.06 mg/L or less.