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- Handeland, S. O., et al.
(author)
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Long-term effects of photoperiod, temperature and their interaction on growth, gill Na+, K+-ATPase activity, seawater tolerance and plasma growth-hormone levels in Atlantic salmon Salmo salar
- 2013
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In: Journal of Fish Biology. - : Wiley. - 0022-1112. ; 83:5, s. 1197-1209
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Journal article (peer-reviewed)abstract
- This study was undertaken to examine the long-term effects of photoperiod, temperature and their interaction on growth, gill Na+,K+-ATPase (NKA) activity, seawater tolerance and plasma growth-hormone levels in Atlantic salmon Salmo salar pre-smolts and smolts. The fish (mean +/- s.e. initial body mass=159 +/- 04g) were reared on two photoperiods (continuous light, LL, and simulated natural photoperiod, LDN, 60 degrees 25 N) and two temperatures (83 and 127 degrees C) from June to May of the following year. Mean body mass was affected by photoperiod, temperature and their interactions. Both temperature groups on LL developed peak levels in gill NKA activity from October to November, 4-5months prior to the natural season for the parr-smolt transformation. Fish at 12 degrees C showed peak levels in NKA activity 4-6weeks before the fish at 8 degrees C. Fish in all four experimental groups showed maximum NKA activity within a similar size range (113-162g). The present findings further indicate that smoltification in S. salar is to some extent driven by size, and that S. salar will develop smolt characteristics, e.g. a marked increase in NKA activity, within a similar size range. Faster-growing S. salar will, thus, reach this size threshold at a relatively younger age. (C) 2013 The Fisheries Society of the British Isles
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| 2. |
- Handeland, S. O., et al.
(author)
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Physiology during smoltification in Atlantic salmon: effect of melatonin implants
- 2013
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In: Fish Physiology and Biochemistry. - : Springer Science and Business Media LLC. - 0920-1742 .- 1573-5168. ; 39:5, s. 1079-1088
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Journal article (peer-reviewed)abstract
- Melatonin implants were used to override natural melatonin rhythm in groups of juvenile Atlantic salmon, Salmo salar, raised at simulated natural photoperiod (SNP) and constant light (LL) from mid-March until end of August. The experiment contained also both sham control (with non-melatonin implants) and control (no implants). No differences were found in the experimental variables between these two control groups. Growth and food intake were negatively affected by melatonin implantation. Overall, higher GH levels were observed in the SNP melatonin-implanted group, whereas no differences in GH levels were seen between the SNP control, LL control, or the LL melatonin-implanted groups. Highest food intake was seen in the LL control group. No differences in food intake were recorded between the LL melatonin-implanted and SNP control groups. Gill Na+, K+, ATPase (NKA) activity was influenced by time as well as the interaction between photoperiod and time. No differences in gill NKA activity or plasma chloride levels following transfer to seawater were seen between the groups with melatonin implants and their controls. Based on the present results, it seems apparent that melatonin does play a role in regulating food intake and growth in Atlantic salmon smolts.
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