1. Smoltification, seawater performance, and maturation in Atlantic salmon (Salmo salar) fed different fat levels.
- Author
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Mota, Vasco C., Verstege, Gerhardus C., Striberny, Anja, Lutfi, Esmail, Dessen, Jens-Erik, Sveen, Lene, Burgerhout, Erik, and Bou, Marta
- Subjects
SMOLTING ,FISH physiology ,ATLANTIC salmon ,FISHERIES ,AQUACULTURE - Abstract
Introduction: The use of recirculating aquaculture systems (RAS) to produce Atlantic salmon smolts has resulted in exceptionally high fish growth rates. However, there are potential negative trade-offs between fast growth and key physiological processes, such as inadequate smoltification and early sexual maturation, which can both be linked to body energy reserves. Methods: This study determined the effect of i) dietary fat levels on Atlantic salmon whole-body fat and fatty acids composition, growth performance and smoltification and ii) a previous dietary regime on seawater growth performance and male early sexual maturation. In freshwater RAS, salmon parr (~19g) were fed 3 fat levels (20, 24, and 28%) over a 14-week period at 12℃. Subsequently, in seawater flow-through systems, smolt (~96g) were fed a control diet (26%) for 12 weeks at 2 temperatures (12 and 16℃). Results: Dietary fat levels resulted in differences in k-factor, fish whole-body fat and fatty acids composition; the low fat diet resulted in fish with a 23% lower whole-body fat when compared to the other two dietary groups at the end of the freshwater phase. These differences in whole-body fat faded at the end of the seawater phase. During the freshwater phase, all three feeds resulted in a comparable growth performance and smoltification indicator values, including k-factor, gill Na
+ , K+ -ATPase, blood serum chloride and smolt index score. In contrast, water temperature resulted in fish body weight differences, where groups reared at 16℃ were larger than those reared at 12℃. Nevertheless, both temperature regimes supported a similar thermal growth coefficient. Smolts grown at 16℃ showed a higher level of the sex steroids androstenedione compared to those at 12℃. However, 11-ketotestosterone and testosterone levels did not differ despite a trend for higher levels at 16℃. Furthermore, testis histology at the final sampling indicated that some individuals showed initial signs of maturation (stage 3). Discussion: In conclusion, varying dietary fat levels (20 - 28%) during the freshwater phase did not influence smoltification or male early sexual maturation during the subsequent grow-out phase. However, a temperature increase from 12 to 16℃ resulted in larger fish and appeared to stimulate early male maturation in some fish individuals. [ABSTRACT FROM AUTHOR]- Published
- 2024
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