Food quality and vgll3 genotype influence reproductive traits in female Atlantic salmon

Age at maturity is an important factor contributing to life-history diversity. In Atlantic salmon, this trait often shows sex-specific variation, but female salmon are seldom included in experimental studies of maturation. As a result, there is a gap in our knowledge of how different genetic and environmental factors affect female maturation. Using a 4-year common-garden experiment, we assessed the influence of diet (low-fat vs. control) and vgll3 (a candidate gene in a genomic region known to influence age at maturity in Atlantic salmon) on maturation and related phenotypic traits of female Atlantic salmon from two 2nd-generation hatchery populations. We found the early-maturation-associated vgll3*E allele to be associated with higher probability of maturation. Heritability of maturation was estimated to be 0.295 with vgll3s contribution to phenotypic variance being [~]2%. In addition, both body size and body condition measured in the spring prior to spawning influenced maturation. Body condition, in turn, was influenced by population and diet. The northern Oulu population and the low-fat diet were associated with lower body condition compared to the southern Neva population and the control diet. Moreover, there was an interaction between population and diet on body condition, suggesting that populations may respond differently to nutrient availability. These results broaden our understanding of the processes underlying maturation and demonstrate that genes and environment interact to shape age at maturity in female Atlantic salmon.