Effect of chronic ammonia
exposure on growth of European seabass (Dicentrarchus labrax)
juveniles
G. Lemarié, A. Dosdat, D. Covès, G. Dutto, E.
Gasset, J. Person-Le Ruyet-2004
Aquaculture, 229(1-4): 479-791
Abstract:
Chronic effects of ammonia were studied in juvenile
seabass, Dicentrarchus labrax (mean WEIGHT=11 g), exposed for 63 days
to eight stable ammonia concentrations, ranging from 0.24 to 0.90 mg l-1
unionised ammonia nitrogen (UIA-N), respectively, from 6.1 to 22.3 mg l-1
total ammonia nitrogen (TA-N). Temperature (21.8 °C), pH (8.0), salinity
(37.0 ppt), and oxygen concentration (over 80% saturation at the outlet)
were maintained constant. Fish were fed using a self-feeder device, and they
were starved during the last 8 days. Mortality of 28.9 and 42.6% occurred
within the first 8 days at the two highest UIA-N concentrations,
respectively, 0.90 and 0.88 mg l-1. From days 0 to 55, a 1.8-fold
increase in weight gain was observed under the 0.90-mg l-1 UIA-N
condition, compared to a 3.4-fold increase in the control. Weight gains were
negatively correlated to ambient ammonia concentrations. Weight loss, or a
transient period of growth stagnation, was observed from the onset of
ammonia exposure to day 13 in seabass exposed to concentrations above 0.43
mg l-1 UIA-N. After day 13, weight gains were observed in all
groups, indicating that the fish were able to adapt to increased ambient
ammonia concentrations over time. By the end of the experiment, plasma
ammonia levels were positively related to ambient ammonia concentrations,
and oxygen consumption recorded in fasting fish was significantly dependent
on ammonia concentrations. In seabass juveniles, the 0.26-mg l-1
UIA-N concentration, under an average pH of 8.0, can be considered as a safe
long-term limit conditions in seawater.
(IFREMER, Station Expérimentale d'Aquaculture,
34250, Palavas les Flots, France, e-mail of A. Dosdat: Antoine.Dosdat@ifremer.fr)