Browsing by Subject "vgll3"

Life-history decisions, and trade-offs, are affected by resource acquisition, which can vary among individuals, and during the life cycle of an individual. In Atlantic salmon (Salmo salar) many life-history decisions, such as age-of-maturity, are strongly associated with two genomic regions, vgll3 and six6. Previously, these genomic regions have been associated with food acquisition in adult sea-run Atlantic salmon; however, this has not yet been studied in juvenile salmon. Furthermore, population density strongly affects the food availability of juvenile salmon through resource competition. Here, using controlled crosses reared in semi-natural stream conditions, I investigated the effect and relationship of life-history genetics and population density on juvenile Atlantic salmon food acquisition. Stomach contents from 148 juvenile Atlantic salmon were quantified for their prey item composition, total number of prey items and dry weight, and environmental and genetic basis of food acquisition were analysed using mixed effects models. Late maturing six6 genotype fish had higher stomach-content dry weights and fuller stomachs than early maturing individuals, in low densities. Furthermore, low density fish were of better condition and had higher growth rates than high density fish. There was no association between six6 and vgll3 genotypes and food acquisition in high densities. The results support the existing knowledge of the negative effect of increasing population density on juvenile Atlantic salmon growth and condition. Furthermore, the density dependent association of six6 and food acquisition suggest a trade-off between early maturation and maximised food acquisition.

In teleost fish, various egg traits play a crucial role in the development, growth, and survival of the offspring and thus affect maternal reproductive success. Atlantic salmon (Salmo salar) is a species where age at maturity, an important life-history trait influencing reproductive success, is under environmental and genetic control. In this study, I assessed how genetics of the vgll3 genotype and the dietary energy content affect egg traits and female maturation rate. The fish used in this study were lab-bred, three-year- old female Atlantic salmon with different vgll3 genotypes fed on one of two diets differing in energy content. The eggs traits included in the study were egg size, lipid, and protein content. Female maturation rate was not affected by the energy level of the diet or the vgll3 genotype. Egg size expressed as egg dry weight differed between females in the two feed treatments. These differences may be attributed to the increased lipid content of the eggs due to the higher fat content of the maternal diet. Females receiving high energy feed had a significantly higher egg lipid content compared to the low energy feed treatment. Females homozygous for the vgll3 allele associated with early maturity had a significantly lower egg lipid content in comparison to the females homozygous for the vgll3 late maturity allele indicating a potential reproductive fitness cost associated with early maturity. No effect of diet or vgll3 was found in egg protein content. This study provides the first evidence of vgll3 not only affecting Atlantic salmon age at maturity, as found in previous studies, but also egg lipids through maternal provisioning of nutrients.