Diet drives performance trade-offs along Atlantic salmon ontology

Abstract

AbstractUnderstanding the mechanistic basis of life-history trade-offs is fundamental for predictive ecology. Variation in resource use is a major determinant of life-history divergence and evolution, and provides a framework for studying life history trade-offs. Contrary to the theory, the documentation of trade-offs between life-history traits that are due to competitive resource allocation is mostly lacking in the wild, which is suggested to be masked by individual differences in resource acquisition. However, this effect has not been empirically demonstrated in free-living populations. In this study, we quantified the diet composition of wild Atlantic salmon (Salmo salar) from different age groups, sampled from marine feeding grounds in the Northeast Atlantic Ocean. We hypothesized that diet composition (i.e., consumption of crustaceansversusfish) has an age-dependent effect on the condition factor, which is a major determinant of age at maturity in Atlantic salmon. We demonstrated an age-dependent reversal of diet effect on condition factor, whereby salmon at younger ages had a higher condition factor when foraging on crustaceans, and a lower condition factor when foraging on fish, andvice versain older age groups. Our results identify resource acquisition as an important process shaping life-history variation in Atlantic salmon via age-dependent performance trade-offs. Our result emphasize the importance of bottom-up trophic effects on maturation dynamics and help to better predict the maturation dynamics of wild populations in the marine environment.