RNA-sequencing to assess the health of wild yellow perch (Perca flavescens) populations from the St. Lawrence River, Canada.

This study aimed to better understand in situ cumulative effects of anthropogenic stressors on the health of St. Lawrence River (QC, Canada) yellow perch populations using high-throughput transcriptomics and a multi-biological level approach. Fish were collected in the upstream fluvial Lake Saint-François (LSF) with low degree of environmental perturbations; Lake Saint-Louis (LSL) considered having a moderate degree of anthropogenic stressors, and Lake Saint-Pierre (LSP) a sector where the perch population has been severely declining. Morphometric results indicated that fish from the downstream LSP showed lower body condition compared to LSF and LSL. Liver transcriptomic responses were assessed by RNA-sequencing. Two hundred and eighty genes were over-transcribed in LSP perch while 200 genes were under-transcribed compared to LSF and LSL. In LSP fish, genes transcripts related to reproduction, retinol, iron, thyroid hormones, oxidative stress, lipid metabolism and immune functions were among the most abundant suggesting that multiple metabolic and physiological pathways were impacted by environmental stressors at this site. Inhibition of liver superoxide dismutase, catalase and glutathione S-transferase activities were also observed at the cellular level. Overall, identified impacted biological pathways in perch from LSP may help understand the precarious state of this population and identify the factors inhibiting its recovery.