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Brook charr is a cold-water species which is highly sensitive to increased water temperatures, such as those associated with climate change. Environmental variation can potentially induce phenotypic changes that are inherited across generations, for instance, via epigenetic mechanisms. Here, we tested whether parental thermal regimes (intergenerational plasticity) and offspring-rearing temperatures (within-generational plasticity) modify the brain transcriptome of Brook charr progeny (fry stage). Parents were exposed to either cold or warm temperatures during final gonad maturation and their progeny were reared at 5 or 8 °C during the first stages of development. Illumina Novaseq6000 was used to sequence the brain transcriptome at the yolk sac resorption stage. The number of differentially expressed genes was very low when comparing fry reared at different temperatures (79 differentially expressed genes). In contrast, 9,050 differentially expressed genes were significantly differentially expressed between fry issued from parents exposed to either cold or warm temperatures. There was a significant downregulation of processes related to neural and synaptic activity in fry originating from the warm parental group vs fry from the cold parental one. We also observed significant upregulation of DNA methylation genes and of the most salient processes associated with compensation to warming, such as metabolism, cellular response to stress, and adaptive immunity. -- Keywords : Brook charr ; epigenetics ; brain ; fry ; temperature.

In the context of climate change, it is crucial to understand whether animals that have been domesticated and (or) selected maintain their abilities to adapt to changes in their thermal environment. Here, we tested how selection for absence of early sexual maturation combined with better growth performance may have impacted thermal resistance and gene expression response in the presence of thermal stress in brook charr Salvelinus fontinalis (Mitchill, 1814). We performed temperature challenge tests on brook charr 0+ juveniles and studied the expression of genes involved in the response to oxidative stress, in synthesis of heat shock proteins, or involved in regulation of apoptosis, in heart and liver tissues. Juveniles from the selected lineage had a higher thermal resistance than controls and a loss of equilibrium occurred on average 1 °C above what was observed for the controls. The relative expressions of catalase and HSP70 were significantly higher in juveniles from the selection program. Overall, thermally sensitive fish were characterized by low mass and length and lower relative expressions of genes associated with stress response. Our results indicate that selection for traits of interests may be indirectly related to the significant lineage effect on growth in early stages of development. -- Keywords : Salvelinus fontinalis (Mitchill, 1814) ; brook charr ; selection ; parental effects ; temperature ; challenge tests.

Many salmonid species are particularly susceptible to chronic and acute temperature changes caused by global warming. We aimed to study the differences in metabolic and transcriptomic responses of a chronic heat stress on a control and selected (absence of early sexual maturation and growth) line of brook charr Salvelinus fontinalis (Mitchill, 1814). We exposed individuals to different temperatures for 35 days (15, 17, and 19 °C). High temperature reduced the growth rate (in length) and the Fulton condition factor. Both maximal metabolic rate and the aerobic scope were higher in fish reared at 17 °C, while they decreased in fish maintained at 19 °C. The relative gene expression of cytochrome c oxidase was lower at 19 °C than at 15 °C. The relative gene expressions of both liver and gill hsp90 was higher at the highest temperature. The standard metabolic rate, while not affected by temperature, was higher for the control line over the selected line. Only in the control line, the relative expression of catalase and of receptor of insulin-like growth factor-1 increased at 19 °C. Our results showed that the selected line was able to cope more effectively with the oxidative stress caused by the rise in temperature. -- Keywords : Salvelinus fontinalis ; brook charr ; chronic thermic stress ; gene expression ; respirometry ; growth ; genetic line.

Fish growth can be modulated through genetic selection. However, it is not known whether growth regulatory mechanisms modulated by genetic selection can provide information about phenotypic growth variations among families or populations. Following a five-generation breeding program that selected for the absence of early sexual maturity and increased growth in brook charr we aimed to understand how the genetic selection process modifies the growth regulatory pathway of brook charr at the molecular level. To achieve this, we studied the regulation of growth traits at three different levels: 1) between lines—one under selection, the other not, 2) among-families expressing differences in average growth phenotypes, which we termed family performance, and 3) among individuals within families that expressed extreme growth phenotypes, which we termed slow- and fast-growing. At age 1+, individuals from four of the highest performing and four of the lowest performing families in terms of growth were sampled in both the control and selected lines. The gene expression levels of three reference and ten target genes were analyzed by real-time PCR. Results showed that better growth performance (in terms of weight and length at age) in the selected line was associated with an upregulation in the expression of genes involved in the growth hormone (GH)/insulin growth factor-1 (IGF-1) axis, including the igf-1 receptor in pituitary; the gh-1 receptor and igf-1 in liver; and ghr and igf-1r in white muscle. When looking at gene expression within families, family performance and individual phenotypes were associated with upregulations of the leptin receptor and neuropeptid Y—genes related to appetite regulation—in the slower-growing phenotypes. However, other genes related to appetite (ghrelin, somatostatin) or involved in muscle growth (myosin heavy chain, myogenin) were not differentially expressed. This study highlights how transcriptomics may improve our understanding of the roles o

Knowledge of the larval ecology of winter-spawning fish from the Estuary and Gulf of St. Lawrence, Canada, remains scarce due to the seasonal ice cover that prevents ichthyoplankton sampling using conventional methods. Two winter-spawning species, Atlantic halibut (AH, Hippoglossus hippoglossus) and Greenland halibut (GH, Reinhardtius hippoglossoides), support the most important groundfish fisheries of this area. In March 2020, the authors captured 10 halibut larvae ranging in size from 5 to 14 mm during an opportunistic survey in the GSL onboard an icebreaking vessel. Of these, eight were AH and two GH. Judging by their very small size, the larvae were only a few days old, suggesting that the spawning grounds are close to the capture sites. This effort constitutes a first step in validating the putative spawning areas for these two important GSL stocks. This knowledge is important for the conservation and sustainable management of these fisheries. -- Keywords : Atlantic halibut ; Greenland halibut ; larval distribution ; larval ecology ; spawning ground ; winter ecology.

Deepwater redfish Sebastes mentella will be among the most important resource-sustaining commercial bottom-fish fisheries in the years to come in the Estuary and Gulf of St. Lawrence (EGSL). In 2011, 2012, and 2013, three strong cohorts were recruited to the stock; their abundance in 2018 was 80 times higher than that of the 1993–2012 period. The main goal of this work was to deepen our knowledge of their growth regulation and metabolism in order to identify molecular indicators and determine how they are influenced by natural environmental conditions. Fish weight and water temperature explained 11% of the variation in relative mRNA levels of specific gene targets in liver and muscle among seven sites where deepwater redfish were captured in the EGSL. The relative expression of liver insulin-like growth factor-1 (igf-1) and white muscle A-chain lactate dehydrogenase (ldh-a) correlate positively with weight, whereas heavy chain muscle myosin (myo), heart citrate synthase (cs), and white muscle pyruvate kinase (pk) correlate negatively. The relative expression of heart cytochrome c oxidase subunit 1 (cox-1) and white muscle igf-1 receptor isoform a (igf-1ra) correlate negatively with temperature. Deepwater redfish from the estuary were smaller than those caught at other sites. Since the growth potential of deepwater redfish was strongly correlated with temperature (being enhanced by higher temperatures), this study suggests an ecological advantage for this species in a climate-warming context.

L’archipel français de saint-Pierre et Miquelon (sPM) est situé à l’est de l’amérique du nord. L’omble de fontaine Salvelinus fontinalis (Mitchill, 1814) est la principale espèce pêchée à la ligne dans les eaux douces de sPM. nous présentons ici une synthèse des études locales et des essais d’élevage réalisés sur ce poisson. nous avons retrouvé des dizaines de documents datant du début des années 1980 qui visaient à élucider sa biologie et son écologie. À cette époque, les premiers essais d’élevage ont été réalisés à Miquelon puis à saint-Pierre, généralement par des bénévoles, et principalement à des fins de repeuplement ou pour développer la pêche spor-tive. ainsi, grâce au travail de nombreux passionnés encadrés occasionnellement par des chercheurs extérieurs, des connaissances ont été acquises sur la biologie, l’écologie et l’élevage de l’omble de fontaine sur l’archipel. Enfin, quelques suggestions pour des travaux ultérieurs (par exemple, la diversité génétique, la connectivité et l’expression génétique) sont présentées. // The French archipelago of Saint-Pierre and Miquelon (SPM) is located in eastern North America. Brook trout Salvelinus fontinalis (Mitchill, 1814) is the key angling species in SPM’s freshwater. Here we provide a synthesis of local studies and rearing trials performed on this fish. Dozens of documents were found dating back from the beginning of the 1980s that aimed to elucidate its biology and ecology. At that time, the first farming trials were conducted in Miquelon and then in Saint-Pierre, generally by volunteers, and mainly for restocking purposes or to develop sport fishing. As a result, thanks to the work of many enthusiasts occasionally supervised by outside researchers, knowledge was acquired on the biology, ecology and farming of brook trout on the archipelago. Finally, some suggestions for further works (e.g. genetic diversity, connectivity and gene expression) are presented. -- Keywords : Angling ; Aquaculture ; Brook trout ; Eco

Characterizing the extent of genetic differentiation among individuals and its distribution across the genome is increasingly important to inform both conservation and management of exploited species. The Greenland Halibut is one of the main demersal fish species to be commercially exploited in Eastern Canada, and accurate information on geographic population structure and local adaptation is required to ensure the long-term presence of this species. We generated high-quality whole-genome sequencing data for 1,297 Greenland Halibut sampled across 32 locations throughout the Northwest Atlantic (from Arctic Canadian and Greenlandic coasts to the Gulf of St Lawrence). Population genetic structure was analyzed, revealing an absence of population differentiation between Canada and west Greenland but significant genetic differentiation between the Gulf of Saint Lawrence and the remainder of the Northwest Atlantic. Except for Gulf of Saint Lawrence, Greenland Halibut thus appear to be panmictic throughout the Northwest Atlantic. Environmental Association Analyses revealed that the environment explained up to 51 % might be replaced by 51% of the differentiation observed between the two stocks, with both ocean-bottom and surface variables (e.g., temperature and oxygen) involved in the observed genomic differentiation. Altogether, these results indicate that phenotypic differences previously observed between the Gulf of Saint Lawrence and the Northwest Atlantic likely resulted from functional adaptive divergence to their respective environmental conditions. Using coalescent simulations, we also assessed how high levels of migration between the two stocks would allow Greenland Halibut to potentially escape unfavorable environmental conditions in the Gulf of Saint Lawrence. In addition to supporting the management of this important exploited species, this work highlights the utility of using comprehensive genomic datasets to characterize the effects of climate change across a w

Applications of mass spectrometry-based metabolomics in food science have developed fast in the last decade. Sample preparation and data processing are critical in non-target/metabolomic workflows but there is currently no standardized protocol for the development of these methods. The impact of data processing parameters or the inclusion of a different matrix is not often taken into account during the selection of an extraction. Thus, this study aimed to investigate the impact of different extractions, e.g., QuEChERS, and data processing on the determination of malachite green metabolites in two different organisms, brook trout and shrimp. The results obtained confirm the need for a harmonized approach for the validation of non-target workflows, as depending on the comparison criteria, the matrix, the mode of ionization or data processing, a different extraction could be chosen. This study also identified for the first time des-methylated leucomalachite green as another metabolite in the two organisms. -- Keywords : Metabolites ; Aquaculture ; Veterinary drugs ; Anti-fungal treatment ; Extraction ; Suspect screening.