Impact of smolt production strategy on vertebral growth and mineralisation during smoltification and the early seawater phase in Atlantic salmon (Salmo salar, L.)

Abstract

This study investigates the effect of different smolt production strategies on vertebral morphology (radiology), composition (mineral content) and mechanical strength (load-deformation testing) in Atlantic salmon (Salmo salar). Rapid-growing underyearling (0+) smolt were compared with slower-growing yearling (1+) smolt and a reference group of wild smolt (w). The underyearling and yearling smolt were transferred to seawater in October 2002 and May 2003, respectively. The underyearling smolt were reared under continuous light and the yearling smolt under natural light during the first twelve weeks in seawater, at ambient temperatures. Thus, the underyearling smolt hit seawater at 13 °C and were reared at 10-13 °C during the early seawater phase, whereas the yearling smolt hit seawater at 7 °C and were reared at 7-10 °C during the early seawater phase. All groups displayed increased longitudinal growth (up to 9% increase in relative length) of the caudal vertebrae during parr-smolt transformation. However, at transfer to seawater, the underyearling smolt had significantly lower vertebral mineral content (0+ 44%, 1+ 47%, w 50%) and higher incidence of deformed vertebrae (0+ 1.5%, 1+ 0%, w 0%), and at twelve weeks after transfer to seawater significantly lower vertebral mineral content (0+ 36%, 1+41%, w 43%), yield-load (0+6492 g, 1+8797 g, w 9150 g) and stiffness (0+7578 g/mm, 1+ 15,161 g/mm, w 20,523 g/mm), and significantly higher incidence of deformed vertebrae (0+ 2.5%, 1+ 0.3%, w 0%). There was a significant correlation between the mineral content and mechanical properties of the vertebrae. The underyearling smolt had significantly elevated plasma concentrations of total Ca, and P and Ca2+ during the parr-smolt transformation and in the early seawater phase.The results show that underyearling smolt may have an increased risk of developing vertebral deformities. It is possible that this risk can be reduced by postponing the start of the short-day treatment. This will reduce the temperature during smoltification, the temperature and daylength during the early seawater phase, and increase the age at smoltification.

Digestive efficiency, free amino acid pools and quality of growth performance in Atlantic salmon (Salmo salar L.) affected by light regimes and vaccine types

“…This is especially important to prevent deformity during the early growth period, as a high protein deposition is important for the growth of the skeleton, comprised of collagen fibres (Rungruangsak-Torrissen et al, unpublished). Moreover, Fjelldal et al (2007a) found that the vertebral body of the Atlantic salmon post-smolts (12 weeks after seawater transfer) with higher mineral concentration, indicating higher mechanical strength (Fjelldal et al 2006), had less compressed morphology than those with lower mineral concentration. Unfortunately, the vertebral protein concentration, vertebral protein turnover rate and fillet composition (P/L ratio) of these fish were not analyzed in Fjelldal et al (2007a).…”

“…The samples were kept frozen at -80°C for later determinations of quality and capacity for protein synthesis in the white muscle (concentrations of RNA and protein, and RNA/protein ratio; Carter et al 1993) and oocyte maturation rate (trypsin-like specific activity, concentrations of RNA and protein, and RNA/protein ratio), as reported in Rungruangsak-Torrissen (2007) and Rungruangsak-Torrissen and Fosseidengen (2007). The experiment was a co-operative project where vertebral growth ) and endocrine secretion (Nordgarden et al 2006) were also studied. Experiment 2: photoperiod and vaccine effects in outdoor cages…”

“…The current work could provide knowledge of the effects of external factors (light regime, vaccine type) on biological responses in protein digestive efficiency and absorption and transport of FAA to the target tissues, such as white muscle, for protein synthesis and growth. These biological parameters could be studied in connection with vertebral growth , endocrine secretion (Nordgarden et al 2006), and growth effect of vaccine types (Oppedal et al 2006), in order to propose the association between these mechanisms in different growth phases, and could provide suggestions for improving the quality of fish growth performance and possible impact of vaccine during continuous light stimulation.…”

“…The parts on ploidy and maturation , vertebral growth , endocrine secretion Nordgarden et al 2006), and vaccine type effect on growth (Oppedal et al 2006) have been published. The current work emphasized efficiency of protein digestion in pyloric caeca, amino acid pools in plasma and white muscle, and protein synthesis capacity in white muscle and oocytes, in order to explain the insight effects of continuous light and vaccine types on protein metabolism by integrating the results from three experiments.…”

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“…Abnormalities in some fish species are reduced with farming practices such as the implementation of appropriate diets and optimized environmental condition (Fjelldal et al, 2005(Fjelldal et al, , 2006Helland et al, 2009;Haga et al, 2011).…”