Data from: Migrate or reside: divergent energetic and immunity programs, ion pumps, and predictive markers of steelhead Oncorhynchus mykiss

Divergent life history strategies occur in Oncorhynchus mykiss, and many populations produce both migrant (anadromous fish that move to the ocean after rearing) and resident (do not migrate and remain in freshwater) individuals. The mechanisms leading to each ecotype are only partially understood; while there may be some heritable mechanisms, it appears that the individual tendency is a plastic trait, influenced by local environment. Hatchery programs aim to mitigate for losses of wild stocks by producing fish that will migrate to the ocean and not compete with wild fish for limited freshwater resources. We compared transcriptome profiles of fish prior to release from a hatchery to those recaptured several days later at their freshwater release site and those recaptured while migrating toward the ocean. We confirmed previous findings of the importance of energetics, gill remodeling, and ion transport capacity for migrants. We also identified a divergent immunity program, in which resident fish induced antiviral defenses, potentially for immune surveillance via dendritic cells in the gills, whereas migrants induced pattern recognition receptors to prepare for seawater entry and the exposure to novel pathogens. Furthermore, we identified a smoltification predictive candidate, protein s100a4, the expression of which was highly correlated with NKA activity, smoltification morphology and migratory behavior. This work provides an ecological immunology comparison for life history types of salmon, as well as a predictive marker that will be used to identify other factors that may direct the trajectory of O. mykiss towards the migrant state.