Effects on the Liver Transcriptome in Baltic Salmon: Contributions of Contamination with Organohalogen Compounds and Origin of Salmon

Hatchery-reared Atlantic salmon (Salmo salar) has been released to support the wild
salmon stocks in the Baltic
Sea for decades. During their feeding migration, salmon are exposed
to organohalogen compounds (OHCs). Here, we investigated the OHC levels
and transcriptome profiles in the liver of wild and hatchery-reared
salmon collected from the Baltic main basin (BMB), the Bothnian Sea
(BS), and the Gulf of Finland (GoF) and examined whether salmon origin
and OHC levels contributed to the hepatic transcriptome profiles.
There were no differences in the OHC concentrations between wild and
reared fish but larger differences between areas. Several transcript
levels were associated with non-dioxin-like polychlorinated biphenyls,
polybrominated diphenylethers, chlordanes, and dichlorodiphenyltrichloroethane
in a concentration-dependent manner. Between wild and reared salmon,
lipid metabolism and related signaling pathways were enriched within
the BMB and BS, while amino acid metabolism was altered within the
GoF. When comparing the different areas, lipid metabolism, environmental
stress and cell growth, and death-related pathways were enriched.
Class coinertia analysis showed that the covariation in the OHC levels
and the transcriptome were significantly similar. These results suggest
that the hepatic transcriptomes in wild and hatchery-reared salmon
are more affected by the OHC levels rather than the origin of salmon.