The impact of elevated water ammonia and nitrate concentrations on physiology, growth and feed intake of pikeperch (Sander lucioperca)

Abstract The ammonia (NH 3 ) and nitrate (NO 3 − ) threshold concentrations in rearing water of juvenile pikeperch ( Sander lucioperca ) were assessed. Pikeperch with an initial mean (SD) weight of 17.7 (4.2) g were exposed to 0.9 (control), 3.6, 5.2, 7.1, 11.2 and 18.9 μM NH 3 in the water for 42 days. Plasma NH 4 + concentrations stayed at control levels (~ 650 μM) up to 11.2 μM NH 3 in the water. At the highest water NH 3 concentration tested, plasma NH 4 + had more than doubled to 1400 μM. Based on the specific growth rate, the EC 10 value for NH 3 was 5.7 μM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO 3 − for 42 days, mean (SD) plasma NO 3 − concentrations increased linearly from 88 (47) to 5993 (899) μM at the highest ambient NO 3 − level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH 3 nor NO 3 − exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na + /K + -ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH 3 concentration of 3.4 μM (0.05 mg NH 3 –N/L), the lower limit of the 95% confidence interval of the EC 10 value for SGR, to ensure proper physiology and growth. For NO 3 − we advise not to exceed 25 mM (350 mg NO 3 − –N/L). This criterion is based on the highest NO 3 − concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO 3 − threshold probably exceeds 25.6 mM.