Alternative migratory tactics in brown trout (Salmo trutta) are underpinned by divergent regulation of metabolic but not neurological genes

The production of alternative morphs within populations is common but the underlying molecular mechanisms remain poorly understood. Many animals, for example, exhibit facultative migration, where two or more alternative migratory tactics (AMTs) coexist within populations. In certain salmonid species, some individuals remain in natal rivers all their lives, whilst others (in particular, females) migrate to sea for a period of marine growth. Here we use RNA-seq profiling to investigate differential gene expression between brown trout smolts (anadromous migratory individuals physiologically prepared to transition to salt water) and residents (mature non-smolts).