Transcriptional profiling of both gills and liver in wild brook charr Salvelinus fontinalis (Mitchill, 1814) populations along a gradient of environmental stressors across the Saint-Pierre and Miquelon archipelago (France).

Natural and anthropogenic environments may have strong impacts on wildlife. The Saint-Pierre and Miquelon archipelago (France) provides a gradient of environmental and anthropogenic pressures relevant to investigate physiological responses in wild brook charr Salvelinus fontinalis populations. This species is the only diadromous species present on the archipelago that is targeted in recreational fisheries, and a better knowledge of native populations is required to support conservation and management activities. We tested the hypothesis that transcriptional phenotypes of brook charr differ among the three main islands of the archipelago and among their respective hydrosystems in response to heterogeneous environmental and anthropogenic pressures. We quantified the expression of 52 candidate genes in both liver and gills for 230 individuals using high-throughput OpenArray qPCR chips developed by the GEN-FISH project. Our results reveal highly spatially structured gene expression patterns. At the island level, local conditions appear to exert specific pressures on brook charr populations. We found a higher expression of genes related to detoxification and oxidative stress in fish captured on Saint-Pierre. In Langlade, the higher expression of genes involved in cellular detoxification could highlight natural geological influences. Transcriptomic responses in gills were more marked than in liver tissue, highlighting the role of gills as a sensitive interface to environmental variations. Overall, the observed signatures underscore the need for more thorough characterization of environmental conditions in Saint-Pierre and Langlade in order to distinguish between anthropogenic and geological effects.