Effects
of chronic ammonia exposure on growth and food conversion efficiency in
juvenile spotted wolffish
A.
Foss, T.H. Evensen, T. Vollen, V. Øiestad-2003
Aquaculture, 228(1-4): 215-224
Abstract:
The effects of chronic un-ionised ammonia (UIA)
exposure on growth and food conversion efficiency (FCE) in spotted wolffish,
Anarhichas minor Olafsen, were examined. Fish with a mean (S.D.)
initial weight 14.2 (5.0) g were reared in shallow raceways (initial
stocking density of 3.9 kg m-2) and exposed to four
concentrations of UIA [0.0006 (control), 0.13 (low), 0.25 (medium) and 0.39
mg l-1 (high)] for 69 days at 8.3 °C, 33 ppt and pH 8.1. Growth
rates were significantly influenced by UIA concentrations, as the control
and low-concentration group performed better than both the medium- and
high-concentration group, and the medium group in turn displayed a higher
growth rate than the high-concentration group throughout the experimental
period. While experiencing negative growth rates in the first period, growth
rates increased and were positive in fish from both the medium and high
group in the second and third period, indicating an adaptation to ambient
UIA. At the end of the experiment, mean weights were 13% and 40% lower at
UIA concentrations of 0.13 and 0.25 mg l-1, respectively, when
compared to the control group, whereas an overall decrease in mean weight
was observed at 0.39 mg UIA l-1 in the experimental period
investigated. The difference in growth performance is mainly attributed to
variations in daily feed consumption, which varied significantly between all
treatments throughout the experiment and decreased with increasing
concentrations of UIA, and to a lesser extent by a decrease in food
conversion efficiency.