Acute toxicity of ammonia to Atlantic salmon (Salmo salar) parr.

1. Atlantic salmon (Salmo salar) parr were exposed to (NH4)2SO4 solutions in static systems with aerated, soft water for 96 hr. The 96 hr-LC50 for un-ionized ammonia (expressed as mg/l NH3-N) ranged from 0.031 (2.1 degrees C) to 0.111 (17.1 degrees C) at pH 6.0 and from 0.030 (1.8 degrees C) to 0.146 (12.5 degrees C) at pH 6.4. 2. No mortality, was found in a KCl solution and a physiological salt solution with chloride concentrations approximately equivalent to the chloride concentration in a NH4Cl solution giving 45% mortality, and to the ammonia concentration in a (NH4)2SO4 solution giving 35% mortality, all solutions tested at pH 6.0 and 2 degrees C.