Turbot juveniles were exposed to four ammonia concentrations [0·17 (L), 0·34 (M), 0·73 (MH) and 0·88 (H) mg l−1 NH3-N] for different exposure durations (28 days minimum to 84 days). Their physiological status and growth performances were compared to a control group [0·004 (C) mg l−1 NH3-N]. No growth was observed in the H group, and by day 57, mass increase in the MH group was only 15% of that in group C. During the first month growth in the L group was similar to that in control group while it was lower (33%) in the M group; afterwards the L and M groups had a similar growth (half that of controls). Accumulation of total ammonia nitrogen (TA-N) in plasma was dependent on ambient ammonia concentrations. Plasma urea levels in ammonia-exposed fish were lower, similar or greater than in controls (depending on ammonia concentration or exposure duration). Osmolarity, Cl– and Na+ plasma concentrations were stable in the L and M groups. The increases in Na+, Cl–, K+ and total Ca concentrations observed by the end of the experiment in the H and MH groups suggest that fish failed to adapt. There was an initial rise in plasma cortisol in all ammonia-exposed groups followed by a return to basal level (1·7–4 ng ml−1) in the L and M groups. In group MH, plasma cortisol peaked at 42 ng ml−1 by day 14, and after a decline at c. 1 month (14 ng ml−1), it rose again.
No Supplementary Data
total ammonia nitrogen;
Document Type: Regular Paper
Laboratoire Adaptation, Reproduction and Nutrition, Ifremer, Centre de Brest, BP 70, 29280 Plouzané, France and
UMR INRA-UNSA 1112 “Rose”, Faculté des Sciences, Université de Nice Sophia-Antipolis, Parc Valrose, 06108 Nice Cédex 2, France
Publication date: 2003-04-01