Effects of salinity
acclimation on pre-smolt growth, smolting and post-smolt performance in
off-season Atlantic salmon smolts (Salmo salar L.)
S.O.
Handeland, S.O. Stefansson-2002
Aquaculture,
209(1-4) : 125-137
Abstract:
The main objective of this study has been to
investigate the effect of salinity acclimation on parr-smolt transformation
and post-smolt performance in off-season Atlantic salmon smolts (Salmo
salar L.). Four groups of potential off-season salmon smolts were raised
under a phase advanced simulated natural photoperiod between 26 July and 14
November. After 9 weeks of photoperiod treatment, salinity in three of the
tanks was changed from freshwater to a salinity of 6.0, 13.1 and 20.0 ppt.
All groups were transferred to full strength seawater on 14 November and
monitored regularly during the next three months. Hypo-osmoregulatory
ability improved in all groups during the first 9 weeks of photoperiod
treatment. A significant increase in gill Na+,K+-ATPase
activity was observed between weeks 9 and 16, with a higher activity in the
20.2 ppt group at week 16. Growth and condition decreased in all saline
groups and no positive effects on post smolt performance were observed.
Final weight after three months in seawater was 13% lower in the 6.0 and
13.1 ppt groups, and 28% lower in the 20.2 ppt group, compared with
controls. Our findings suggest that acclimating Atlantic salmon to saline
water during off season smolting has no positive consequences, and is
probably not necessary to stimulate the development of hypo-osmoregulatory
ability and increase gill Na+,K+-ATPase activity
during smolting or improve post-smolt growth.
(Department of Fisheries and Marine Biology,
University of Bergen, High Technology Centre, N-5020 Bergen, Norway, Tel.:
+47-55-58-45-45; fax: +47-55-58-44-50, e-mail: Sigurd.Handeland@ifm.uib.no)