Standard metabolic rate does not associate with age-at-maturity genotype in juvenile Atlantic salmon

Atlantic salmon (Salmo salar) is a species with diverse life-history strategies, to which the timing of maturation contributes considerably. Recently, the genome region including the gene vgll3 has gained attention as a locus with a large effect on Atlantic salmon maturation timing, and recent studies on the vgll3 locus in salmon have indicated that its effect might be mediated through body condition and accumulation of adipose tissue. However, the cellular and physiological pathways leading from vgll3 genotype to phenotype are still unknown. Standard metabolic rate is a potentially important trait for resource acquisition and assimilation and we hypothesized that this trait, being a proxy for the maintenance energy expenditure of an individual, could be an important link in the pathway from vgll3 genotype to maturation timing phenotype. As a first step to studying links between vgll3 and the metabolic phenotype of Atlantic salmon, we measured the standard metabolic rate of 150 first-year Atlantic salmon juveniles of both sexes, originating from 14 different families with either late-maturing or early-maturing vgll3 genotypes. No significant difference in mass-adjusted standard metabolic rate was detected between individuals with different vgll3 genotypes, indicating that juvenile salmon of different vgll3 genotypes have similar maintenance energy requirements in the experimental conditions used and that the effects of vgll3 on body condition and maturation are not strongly related to maintenance energy expenditure in either sex at this life stage.