Effects of sodium and calcium on acute toxicity of un-ionized ammonia to Atlantic salmon and lake trout

Acute, static 6-hour toxicity tests were conducted on two sizes each of lake trout and Atlantic salmon in the presence of three levels each of NaCl and CaCl₂. Calcium did not protect smolts from NH₃ toxicity but had no effect on the tolerance of Atlantic salmon fry to NH₃. Both cations increased the tolerance of 8-g lake trout fingerlings to NH₃, but neither significantly affected the toxicity of NH₃ to 0.9-g lake trout fry. These results suggest that the mitigating effects of solution cations of NH₃ toxicity may be related to species, size, and life stage.