Life-history genotype explains variation in migration activity in Atlantic salmon ( Salmo salar )

Abstract

One of the most well-known life-history continuums is the fast–slow axis, where ‘fast’ individuals mature earlier than ‘slow’ individuals. ‘Fast’ individuals are predicted to be more active than ‘slow’ individuals because high activity is required to maintain a fast life-history strategy. Recent meta-analyses revealed mixed evidence for such integration. Here, we test whether known life-history genotypes differ in activity expression by using Atlantic salmon ( Salmo salar ) as a model. In salmon, variation in Vgll3, a transcription cofactor, explains approximately 40% of variation in maturation timing. We predicted that the allele related to early maturation ( vgll3 *E) would be associated with higher activity. We used an automated surveillance system to follow approximately 1900 juveniles including both migrants and non-migrants (i.e. smolt and parr fish, respectively) in semi-natural conditions over 31 days (approx. 580 000 activity measurements). In migrants, but not in non-migrants, vgll3 explained variation in activity according to our prediction in a sex-dependent manner. Specifically, in females the vgll3 *E allele was related to increasing activity, whereas in males the vgll3 *L allele (later maturation allele) was related to increasing activity. These sex-dependent effects might be a mechanism maintaining within-population genetic life-history variation.