Schram, E; Roques, JAC; van Kuijk, T; Abbink, W; van De Heul, Jan; de Vries, P; Bierman, S; van De Vis, H; Flik, G
The ammonia (NH3) and nitrate (NO) 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 mu M NH3 in the water for 42 days. Plasma NH4+ concentrations stayed at control levels (similar to 650 mu M) up to 112 mu M NH3 in the water. At the highest water NH3 concentration tested, plasma NH4+ had more than doubled to 1400 mu M. Based on the specific growth rate, the EC10 in value for NH3 was 5.7 mu M. When pikeperch (initial mean (SD) weight of 27.0 (49) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 61,102 15.8 and 25.6 mM NO3 for 42 clays, mean (SD) plasma NO3 concentrations increased linearly from 88 (47) to 5993 (899) mu M at the highest ambient NO3 level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO-I exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osrnolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3A mu M (0.05 mg NH3-N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3- we advise not to exceed 25 niM (350 mg NO3--N/L). This criterion is based on the highest NO3- concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO threshold probably exceeds 25.6 mM. (C) 2013 Elsevier B.V. All rights reversed.