Toxicity of ammonia to Atlantic salmon ( Salmo salar L.) in seawater—Effects on plasma osmolality, ion, ammonia, urea and glucose levels and hematologic parameters

Abstract

Atlantic salmon ( Salmo salar L.) (369 ± 70 g) were exposed to nominal water ammonia levels of 0.5 (control), 3, 22, 40, 112 and 255 μg/l NH 3-N (0.05–25.3 mg/l TA-N; total ammonia-N) in running seawater at 8–9°C, 33–35% salinity, pH 7.8–7.9 and 6.3–9.7 mg/l O 2. Blood plasma TA, urea, glucose, osmolality and ion levels and blood hematocrit (Hct), erythrocyte osmotic fragility (EOF), red blood cell count (RBC) and mean cell volume (MCV) were measured after 2–3 and 14–15 days of exposure. Plasma TA increased linearly with the water TA level. Plasma urea generally decreased with increasing water ammonia level, except for at 225 μg/l NH 3-N. At this acutely toxic ammonia level, plasma osmolality, Na +, Cl −, Mg 2+, urea and TA levels were largely increased; plasma glucose and Ca 2+ moderately increased and Hct decreased; and all fish were dead within 6 days of exposure. Plasma glucose, osmolality and ion levels, and blood Hct, RBC, EOF and MCV were not affected within 14–15 days of exposure to 22 μg/l NH 3-N.