Temporal dynamics of DNA methylation patterns in response to rearing juvenile steelhead (Oncorhynchus mykiss) in a hatchery versus simulated stream environment

Here we used a controlled experiment to investigate whether hatchery-rearing conditions can influence patterns of DNA methylation in steelhead and directly assessed the stability of these changes over time in fish with known genetic backgrounds. For this experiment, embryos from 22 families of Methow River steelhead were split across two rearing treatments; either traditional hatchery rearing or a simulated stream rearing environment. The families were reared for one year before merging the two treatments for an additional year of rearing in a common tank environment. DNA methylation patterns were examined in the liver of male juveniles at the end of the rearing treatment in the first year as well as in sexually immature males after common hatchery rearing in the second year. Further, we analyzed DNA methylation in the sperm of males that matured at approximately two years of age to assess the potential of environmentally-induced changes to be passed to offspring.