Integrative transcriptomic and microbiome insights into the growth divergence and osmoregulatory responses of juvenile rainbow trout (Oncorhynchus mykiss) in seawater

Rainbow trout (Oncorhynchus mykiss) aquaculture is mainly conducted in freshwater worldwide. Seawater farming can conserve freshwater resources, but salinity fluctuations may cause physiological stress. Salinity is an important environmental factor that regulates growth, metabolism, and intestinal microbiota homeostasis in teleost fish. In this study, biochemical assays, RNA-seq, and 16S rRNA sequencing were used to investigate the regulatory mechanisms of the microbiota-gut-brain axis associated with growth divergence, stress resistance, and metabolic functions in rainbow trout reared in freshwater and in fast- and slow-growing individuals under seawater conditions.