Ž.
Aquaculture 178 1999 171–187
ž
Effects of carbon dioxide on Atlantic salmon Salmo
/
salar L. smolts at constant pH in bicarbonate rich
freshwater
Sveinung Fivelstad
a,)
, Anne Berit Olsen
b
, Hilde Kløften
a
,
Hanne Ski
a
, Sigurd Stefansson
c
a
Laboratory of the EnÕironment, Department of Engineering, Bergen College, Nygardsgaten 112, P.O. Box
˚
7030, N-5020 Bergen, Norway
b
National Veterinary Institute Bergen, Minde Alle 10, P.O. Box 40, N-5826 Minde, Norway
c
Department of Fisheries and Marine Biology, UniÕersity of Bergen, Bergen High Technology Centre, N-5020
Bergen, Norway
Accepted 25 March 1999
Abstract
Ž.Ž .
Atlantic salmon Salmo salar L. smolts mean weight 53 g in bicarbonate rich freshwater
were exposed to three levels of carbon dioxide partial pressure for 62 days in an open flow
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system: 2 mm Hg control , 5 mm Hg medium and 9 mm Hg high . Water temperature was
y
1
Ž
3–78C and oxygen levels above 9 mg l . All groups were transferred to normal seawater 34‰
.
salinity on day 63. The seawater period lasted for 123 days. After 3 days, a transient but
significant increase in the mean plasma cortisol concentration of the high carbon dioxide group
Ž
y
1
.
32 mg l ; P s9 mm Hg was observed. The respiration frequency of the high CO group
CO 2
2
was significantly increased during the freshwater period from days 0 to 58. The respiration
Ž
y
1
.
frequency of the medium group 19 mg l ; P s5 mm Hg was intermediate between the
CO
2
Ž
y
1
.
control 7 mg l ; P s2 mm Hg and the high group. There were no significant differences in
CO
2
plasma glucose or haemoglobin levels between groups. Haematocrit levels of smolts in the high
CO group were slightly increased after 3 days and significantly increased after 25 days,
2
compared to the control group. After 61 days, however, no significant differences between groups
were found. The mean plasma chloride concentrations of smolts in the medium and high CO
2
groups were significantly reduced after both 3 and 61 days of exposure. After 62 days, there were
no significant differences in mean fish length between the groups. The mean weight was reduced,
although not significantly in the high group. The mean condition factors in the medium group and
Ž.
high groups 5 and 9 mm Hg, respectively were though significantly reduced. Nephrocalcinosis
)
Corresponding author. Tel.: q47-5558-7500; Fax: q47-5558-7790; E-mail: sveinung.fivelstad@hib.no
0044-8486r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved.
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PII: S0044-8486 99 00125-8