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Arctic waters are warming rapidly due to climate change, which is altering the timing of seasonal sea ice dynamics. Summer ice breakup provides a critical productivity bloom that consumers depend on. Arctic char Salvelinus alpinus undertake seasonal migrations to marine waters presumably to exploit this prey pulse. However, specific migratory timing and residency of char relative to breakup is largely unknown. To investigate char movement, individuals were tagged with acoustic transmitters in 2017 (n = 58) and 2018 (n = 52) within Tremblay Sound, Nunavut, Canada, resulting in 625482 detections. Generalized linear models were used to relate multiple movement metrics to ice conditions as well as biological and temporal factors. Char exhibited multiple migratory patterns (chronologies), by which fish either migrated to/from rivers within Tremblay Sound (n = 67), rivers in external systems (n = 35), or a combination of both (n = 8). Fish that migrated exclusively from external systems were longer (~14 cm) than fish exhibiting other chronologies. Migration timing was related to chronology and preempted the specific ice-off date. Fish migrating from rivers within Tremblay Sound entered the marine environment ~7.5 d before the start of ice-off, while external migrants entered ~21 d after ice-off start. Differing migratory chronologies highlight the complexity of char migrations and may indicate the presence of subpopulations or potential ontogenetic shifts in migration behavior. Our study underscores the importance of the brief ice-free season, with potential implications for climate change resilience and management of this important resource in a changing Arctic.

Fisheries managers call for more nuanced understandings of complex interactions between exploitation and environmental variability, especially in data poor settings. We develop a bioeconomic model for the Arctic char (Salvelinus alpinus) out of Nain, northern Labrador, incorporating climate variability into growth. We derive parameters necessary for the bioeconomic analysis through optimization and identify optimal equilibrium conditions for the model with and without climate variability. Accounting for variability results in a slightly higher optimal harvest, fishing effort and stock. We find an optimal effort of 591 fishing weeks and harvest of 156 920 kg for 2014, suggesting that both were below optimal. We further find that increased temperature leads to higher optimal effort and net benefits at steady state. Despite numerous uncertainties, data and knowledge gaps limiting the accuracy of our estimates, this is the first effort to identify the equilibrium harvesting conditions for this currently uneconomic, yet socially and culturally important fishery. The methodology can be applicable to other data-deficient fisheries with similar challenges and unknowns, to advance the understanding of socially optimal harvesting and interactions with environmental variability.

Analysing the geographical distribution of evolutionary linages can reveal the potential locations of past refugia and colonisation routes and thus can improve understanding of current patterns of genetic variation and adaptive potential. We analysed 94 full mitogenome sequences to assess phylogeographic relationships amongst ten Arctic char (Salvelinus alpinus) populations, from western Greenland, eastern Greenland, Iceland and Norway. In addition, we excised D-loop sequences, which were combined with previously published data in order to provide a circumpolar phylogeographical overview. In western Greenland, a secondary contact zone between Arctic and Atlantic evolutionary lineages was identified, spanning >1000 km, which geographically parallels a similar contact zone in Labrador, Canada. In eastern Greenland, Iceland and Norway, the Atlantic lineage was exclusively observed, whereas the northernmost western Greenland populations belonged to the Arctic lineage. The Arctic and Atlantic lineages were estimated to have diverged ca. 400,000 years BP, corresponding to the onset of the Saale glaciation, whereas the time of the most recent common ancestor (TMRCA) of the Arctic lineage was ca. 15,000 years BP. The Atlantic lineage comprised two subclades, with an estimated TMRCA of 60,000 BP, suggesting a complex history involving cryptic refugia or multiple recolonisations. Codon-based tests revealed no evidence for positive selection within the 13 coding genes, indicating that there are no mitochondrial genetic adaptations within or between lineages. Higher genetic diversity observed within the contact zone likely correlates with higher standing genetic variation that could contribute to adaptive responses and morphological diversification, which Arctic char is renowned.

Although intestinal microbial communities from anadromous Arctic char (Salvelinus alpinus (Linnaeus, 1758)) in Kitikmeot, Nunavut, Canada, differ depending on the timing and location of capture, determinants of gut microbiota in other wild Arctic salmonids are largely unknown. Using high-throughput 16S rRNA gene sequence data, we compared intestinal microbiota from Arctic char to those from a related and sympatric salmonid, lake whitefish (Coregonus clupeaformis (Mitchill, 1818)). Shifts in lake whitefish gut microbial community composition were observed between brackish water and freshwater, similar to impacts of salinity reported previously for Arctic char. Despite these similarities, gut community profiles for the two salmonids differed, with whitefish having higher diversities and increased proportions of taxa affiliated with potential pathogens. Geography seemed to have a greater impact on freshwater whitefish gut microbiota than on corresponding Arctic char. Additionally, microbiota diversity was significantly more affected by feeding behavior in whitefish compared with sympatric Arctic char. As sampled whitefish were at their northern range limits and grew slowly, we speculate that they, and their microbial consortia, could be more vulnerable to certain abiotic and biotic factors than Arctic char, which are well adapted to conditions found in these high latitude environments and have the most northern distribution of any freshwater fish.

Arctic char drying at a camp near Clyde River, Nunavut, Canada.Land acknowledgments—statements about the Indige­nous Peoples on whose lands others live and work—have become increasingly common in A...

Distinguishing neutral and adaptive genetic variation is one of the main challenges in investigating processes shaping population structure in the wild, and landscape genomics can help identify signatures of adaptation to contrasting environments. Arctic Char (Salvelinus alpinus) is an anadromous salmonid and the most harvested fish species by Inuit people, including in Nunavik (Québec, Canada), one of the most recently deglaciated regions in the world. Unlike many other anadromous salmonids, Arctic Char occupy coastal habitats near their natal rivers during their short marine phase restricted to the summer ice‐free period. Our main objective was to document putatively neutral and adaptive genomic variation in anadromous Arctic Char populations from Nunavik and bordering regions to inform local fisheries management. We used genotyping by sequencing (GBS) to genotype 18,112 filtered single nucleotide polymorphisms (SNP) in 650 individuals from 23 sampling locations along >2000 km of coastline. Our results reveal a hierarchical genetic structure, whereby neighboring hydrographic systems harbor distinct populations grouped by major oceanographic basins: Hudson Bay, Hudson Strait, Ungava Bay, and Labrador Sea. We found genetic diversity and differentiation to be consistent both with the expected postglacial recolonization history and with patterns of isolation‐by‐distance reflecting contemporary gene flow. Results from three gene–environment association methods supported the hypothesis of local adaptation to both freshwater and marine environments (strongest associations with sea surface and air temperatures during summer and salinity). Our results support a fisheries management strategy at a regional scale, and other implications for hatchery projects and adaptation to climate change are discussed.

Climate change is having myriad effects on Arctic marine ecosystems and food webs. Anadromous Arctic Char, Salvelinus alpinus (Linnaeus, 1758), feed intensively at sea during summer. In Cumberland Sound, Nunavut, Canada, there has been a recent increased availability of a forage fish, Capelin. To investigate changes over time in Arctic Char foraging, we assessed Arctic Char trophic niche from 2002 to 2011 using stomach content analysis and stable isotope analysis (δ13C and δ15N) of muscle tissue from two river/lake systems, Isuituq and Kipisa. We also compared population characteristics by calculating Fulton’s condition factor (K) and by fitting von Bertalanffy growth curves with length-at-age data. Results revealed Capelin were newly present in the diets of Arctic Char in 2011, describing a shift from a primarily invertebrate-based to a fish-based diet. No trend in δ15N over time suggests that the trophic level of Arctic Char has not changed; however, the δ15C for both systems converged in 2011 on a value suggestive of feeding on Capelin. Growth curves and length-at-age analyses suggest that foraging on Capelin may have increased individual growth. Changes in the growth and condition of Arctic Char in this region could have significant economic and cultural implications.

Throughout their range, anadromous Arctic Char (Salvelinus alpinus (Linnaeus, 1758)) support commercial, recreational, and subsistence fisheries that are important economically, socially, and culturally. However, drivers of interannual variation in survival in this species remain poorly understood. Here, we aimed to quantify the impact of environmental and biological parameters on the survival probability of anadromous Arctic Char near the community of Cambridge Bay, Nunavut, Canada. To do so, we tracked 183 Arctic Char tagged with acoustic transmitters and used capture–mark–recapture methods to estimate survival probabilities over six years. Annual survival probabilities for individuals was high, varying between 0.79 and 0.88, whereas recapture probabilities varied between 0.64 and 0.90. Interannual variation in survival probability was low and neither the environmental (air temperature and sea ice cover) nor biological (sex) variables influenced survival probability. These estimates suggest that annual survival probability is high for anadromous adult Arctic Char in the Cambridge Bay area, despite clear differences in the ice cover melt date among years. These results further our understanding of the demographic parameters of Arctic Char in the region, which will be important for future assessments of the sustainability of commercial fisheries as well as for predicting population responses to a rapidly changing Arctic.

We analyzed Arctic char (Salvelinus alpinus (Linnaeus, 1758)) stable isotope ratios and fatty acid composition from two geographically proximal Nunavut lakes, Qasigiyat and Iqalugaarjuit, to determine if anadromous and resident Arctic char occupied different trophic niches. Resident Arctic char had lower δ13C and δ34S, indicative of freshwater feeding, compared with anadromous individuals. Significantly lower δ15N of residents suggests the ecotypes feed at different trophic levels. Significantly wider δ13C and δ15N ranges in residents implied a broader trophic niche or a wider range in baseline prey isotope values. Results also provide further evidence for resident use of the estuarine environment in Qasigiyat. Immature Arctic char occupy a different trophic niche than both resident and anadromous fish within Iqalugaarjuit, but this relationship is less clear in Qasigiyat. Distinct stable isotope and fatty acid profiles indicate that resident and anadromous Arctic char have distinct trophic niches: marine for anadromous, freshwater for resident. Immature Arctic char seem to occupy a distinct niche from both anadromous and resident fish, which likely relates to use of both freshwater and estuarine environments, depending on developmental stage. We show the first evidence of the fatty acid differences and niche segregation between sympatric anadromous and resident ecotypes in Arctic char.

The lake ecology of high-latitude fishes is strongly influenced by seasonal feeding opportunities and environmental stochasticity in Arctic environments. Arctic Charr (Salvelinus alpinus (Linnaeus, 1758)) populations are prevalent throughout the Arctic and show multiple life history strategies across their range. Unlike Old World populations, the lake ecology of Arctic Charr populations on south Baffin Island remains poorly defined. We examined the comparative seasonal lake ecology of two differing Arctic Charr populations (anadromous and landlocked) in Cumberland Sound, Nunavut. Anadromous Charr showed no evidence of feeding occurring within freshwater once they began seaward migrations. Anadromous Charr achieve sexual maturation at a larger size and younger age than landlocked Charr. Landlocked Charr used more lake habitats than anadromous Charr with feeding opportunities as an apparent influence on habitat selection. Landlocked Charr fed year round. They adopted a cannibalistic feeding strategy in the winter but consumed a variety of prey items in the fall. Littoral habitat was found to be important to all sizes of Charr in both seasons. Smaller anadromous Charr (

Arctic char Salvelinus alpinus is an important cultural and subsistence resource for Inuit communities. Muscular infections by microsporidia were diagnosed for the first time in Arctic char originating from 2 different lakes in Nunavik (Quebec, Canada). The consumption of these infected fish was associated with digestive tract disorders in people. To better characterize microsporidiosis in these char populations, a cross-sectional study was conducted on 91 fish. The microsporidium was classified as a member of the Microsporidium collective genus by morphological evaluation and phylogenetic analysis using small subunit ribosomal DNA sequence data. The presence and severity of infection were determined histologically. Microsporidian infection occurred in 61% of the fish (56/91) and was significantly associated with an increase in their age, length and weight. The severity of infection (percentage of muscle area affected by microsporidia) was mild in most cases (

Mobile consumers often match their movements to short-term resource pulses. In the Arctic, seasonal ice breakup facilitates an ephemeral productivity pulse exploited by marine consumers. The migration of anadromous Arctic char (Salvelinus alpinus) to marine waters occurs around the beginning of ice breakup, but the precise timing of movement is equivocal and current evidence is conflicting. To investigate the migratory timing of Arctic char, 34 individuals were tagged with acoustic telemetry transmitters within Tremblay Sound, Nunavut, Canada in two successive years. All tagged fish entered the marine environment before the coastal ice-off date (mean ± SE: 7.56 ± 0.56 days). Further movement metrics revealed that char utilized much of the sound before the ice-off date, with only slightly higher mean home ranges (0.3 km2 larger) and residency indices (by ~ 0.05) during the period following the ice-off date than prior. Such entry and use of marine waters prior to ice breakup may impart energetic benefits to early migrants, maximizing exploitation of the short, anticipated pulse of productivity. The current study provides a unique example of resource tracking that could confer heightened fitness to a marine consumer in the rapidly warming high Arctic.

Arctic warming associated with global climate change poses a significant threat to populations of wildlife in the Arctic. Since lipids play a vital role in adaptation of organisms to variations in temperature, high-resolution mass-spectrometry-based lipidomics can provide insights into adaptive responses of organisms to a warmer environment in the Arctic and help to illustrate potential novel roles of lipids in the process of thermal adaption. In this study, we studied an ecologically and economically important species-Arctic char (Salvelinus alpinus)-with a detailed multi-tissue analysis of the lipidome in response to chronic shifts in temperature using a validated lipidomics workflow. In addition, dynamic alterations in the hepatic lipidome during the time course of shifts in temperature were also characterized. Our results showed that early life stages of Arctic char were more susceptible to variations in temperature. One-year-old Arctic char responded to chronic increases in temperature with coordinated regulation of lipids, including headgroup-specific remodeling of acyl chains in glycerophospholipids (GP) and extensive alterations in composition of lipids in membranes, such as less lyso-GPs, and more ether-GPs and sphingomyelin. Glycerolipids (e.g., triacylglycerol, TG) also participated in adaptive responses of the lipidome of Arctic char. Eight-week-old Arctic char exhibited rapid adaptive alterations of the hepatic lipidome to stepwise decreases in temperature while showing blunted responses to gradual increases in temperature, implying an inability to adapt rapidly to warmer environments. Three common phosphatidylethanolamines (PEs) (PE 36:6|PE 16:1_20:5, PE 38:7|PE 16:1_22:6, and PE 40:7|PE 18:1_22:6) were finally identified as candidate lipid biomarkers for temperature shifts via machine learning approach. Overall, this work provides additional information to a better understanding of underlying regulatory mechanisms of the lipidome of Arctic organisms in the face of near-future warming.

Contemporary intraspecific patterns of genetic variation reflect the historical effects of population subdivision–expansion and forces like drift, gene flow, and selection. We investigated the population structure of anadromous Arctic char (Salvelinus alpinus) in the Lower Northwest Passage (LNWP), Nunavut, using 3074 genome-wide single nucleotide polymorphisms markers (SNPs). Overall, the genetic differentiation was weak to moderate among 18 sampling locales (global FST= 0.037). Populations were structured hierarchically, with a deeper genetic division between King William Island (global FST= 0.018) and mainland populations ∼200 km away to the south (global FST= 0.018), and some evidence of genetic subgroups within the former. These findings suggest a role for char migratory behaviour in shaping contemporary genetic population structure, with demographic modelling favouring an isolation with migration over a strict isolation scenario. Twenty-two SNPs were identified as potentially under divergent selection with putative functions including neurotransmission and bone development and growth during late embryogenesis. Our study is the first survey of Arctic char in the LNWP using genomics and provides baseline data for the development of a sustainable fishery within this region.

Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char (Salvelinus sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length‐frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present‐day char populations. Although some lakes exhibit bimodal size distributions, using model‐based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha‐1), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food‐limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation., In this study, we described the morphological and genetic diversity of seven populations of arctic char with varying length‐frequency distributions across two distinct groups of lakes in northern Alaska. Although some lakes exhibit multimodal size distributions, using model‐based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genetic analyses demonstrated differences among lake groups, but within lake groups and within individual lakes, genetic differentiation was not related to total body length.

Arctic char (Salvelinus alpinus) and brook trout (Salvelinus fontinalis) hybridize and their offspring is viable and fertile. This may be a real treat for the native European stocks of Arctic char which gene pools might be unintendedly contaminated with the genetic elements of brook trout. On the other hand, hybrids of these two species are appreciated by customers and have some potential for the aquaculture. Moreover, Salvelinus hybrids and backcross individuals are interesting models in the research focused on influence of hybridization on the genomic organization and chromosome rearrangements. Thus, the main goal of the present study was to examine chromosomes of Arctic char × brook trout F1, F2 hybrids and backcross individuals and compare with genomic information concerning parental species to recognize karyotypic changes provoked by the hybridization events. Application of conventional and molecular (FISH) techniques allow to identify characteristic chromosomes for both parental species in the hybrid progeny and show multiplicity of cytotypes among different types of crosses with variability in structure and number of chromosome (81–85) and chromosome arm (99–101). Chromosome fragment was detected in the karyotype of one F1 and one backcross individual and the presence of one triploid (3n) fish was documented. Occurrence of chromosomes containing internally located telomeric sequences (ITS) inherited after brook trout or both parental species was shown in F1 and backcross progeny. Moreover, additional CMA3-positive signal on chromosome from Arctic char pair no. 2 in F1 fish and interstitially located active NOR visible on subtelo-acrocentric (F2 hybrid) and acrocentric (Sf × H individual) chromosomes were detected. Described polymorphic chromosomes together with specific, interstitial location of CMA3-positive found in F2 and Sf × H hybrids and DAPI-positive regions observed in H × Sa fish at different uniarmed chromosomes pair presumably are remnants of chromosomal rearrangements. Provided results strongly indicate that the hybridization process influenced the genome organization in the Salvelinus hybrid progeny.

Despite low species diversity and primary production, trophic structure (e.g., top predator species, predator size) is surprisingly variable among Arctic lakes. We investigated trophic structure in lakes of arctic Alaska containing arctic char Salvelinus alpinus using stomach contents and stable isotope ratios in two geographically-close but hydrologically-distinct lake clusters to investigate how these fish may interact and compete for limited food resources. Aside from different lake connectivity patterns ('leaky' versus 'closed'), differing fish communities (up to five versus only two species) between lake clusters allowed us to test trophic hypotheses including: (1) arctic char are more piscivorous, and thereby grow larger and obtain higher trophic positions, in the presence of other fish species; and, (2) between arctic char size classes, resource polymorphism is more prominent, and thereby trophic niches are narrower and overlap less, in the absence of other predators. Regardless of lake cluster, we observed little direct evidence of arctic char consuming other fishes, but char were larger (mean TL = 468 vs 264 mm) and trophic position was higher (mean TP = 4.0 vs 3.8 for large char) in lakes with other fishes. Further, char demonstrated less intraspecific overlap when other predators were present whereas niche overlap was up to 100% in closed, char only lakes. As hydrologic characteristics (e.g., lake connectivity, water temperatures) will change across the Arctic owing to climate change, our results provide insight regarding potential concomitant changes to fish interactions and increase our understanding of lake trophic structure to guide management and conservation goals.

The Canadian Arctic is a unique food producing region. Much of the food produced in the Canadian Arctic has a strong tie with Indigenous cultures and communities, is produced or harvested in a pristine environment, and features species not commonly consumed in other parts of Canada. Building upon previous work and using data from a survey of Canadian consumers featuring a discrete choice experiment positioned around a seafood purchasing decision (Arctic Char), we use a latent class model to examine heterogeneity in consumer responses to Arctic food. We identify three groups (classes) of consumers who differ in the relative importance placed on geographic origin, Indigenous origin, wild harvested (vs. farmed), and certification for sustainability and authenticity. A class membership model explores the sociodemographic and psychographic characteristics differentiating consumers across these three groups, including food neophobia and consumers’ prior perceptions of the Arctic as a food producing region with respect to quality expectations, environmental and social impacts, Indigenous cultural origins, health, moral and price concerns. Our analysis sheds light onto Indigenous cultural origin as a novel type of credence attribute. We discuss implications for the Arctic food sector and for regional certification initiatives. L′Arctique canadien est une region de production alimentaire unique. La plupart des aliments produits dans l′Arctique canadien ont un lien etroit avec les cultures et les communautes autochtones, sont produits ou recoltes dans un environnement vierge et contiennent des especes qui ne sont pas couramment consommees dans d′autres regions du Canada. En nous appuyant sur des travaux anterieurs et en utilisant les donnees d′une enquete aupres des consommateurs canadiens comportant une experience de choix discret positionnee autour d′une decision d′achat de fruits de mer (omble chevalier), nous utilisons un modele de classe latente pour examiner l′heterogeneite des reponses des consommateurs aux aliments de l′Arctique. Nous identifions trois groupes (classes) de consommateurs qui different par l′importance relative accordee a l′origine geographique, l′origine autochtone, l′aspect sauvage (par rapport a l'elevage) et la certification pour la durabilite et l′authenticite. Un modele d′appartenance a une classe explore les caracteristiques sociodemographiques et psychographiques qui differencient les consommateurs de ces trois groupes, y compris la neophobie alimentaire et les perceptions anterieures des consommateurs de l′Arctique en tant que region de production alimentaire en ce qui concerne les attentes de qualite, les impacts environnementaux et sociaux, les origines culturelles autochtones, problemes de sante, de moralite et de prix. Notre analyse met en lumiere l′origine culturelle autochtone en tant que nouveau type d′attribut de credibilite. Nous discutons des implications pour le secteur alimentaire de l′Arctique et pour les initiatives de certification regionales.

Flavobacterium species cause significant disease in salmonid farming worldwide, typically seen as mortality in sac fry and later as necrosis and ulceration in fingerlings and fry. In this study, we sampled Atlantic salmon Salmo salar and Arctic char Salvelinus alpinus from 5 Icelandic fish farms in 2014 and 2017, where flavobacteria were suspected to cause disease. The objective of the study was to identify and characterise the bacteria by sequencing the 16S rRNA gene and multilocus sequence type housekeeping genes. We found 5 distinct groups of flavobacteria: 3 that were homogeneous and appeared to persist in the fish farms between 2014 and 2017 and 2 that were heterogeneous and transient. Flavobacterium psychrophilum could be isolated from diseased Arctic char from all 5 fish farms in both 2014 and 2017. However, while the other 4 Flavobacterium sp. groups were isolated from Atlantic salmon, water and roe, F. psychrophilum could not be isolated from these samples. This indicates that flavobacteria other than F. psychrophilum may be the primary cause of fin and tail rot in Icelandic Atlantic salmon fry.

As the Arctic rapidly warms, sub-Arctic species such as the Atlantic salmon (Salmo salar) are expected to shift their distributions into the Arctic, potentially facilitating interaction with native Arctic species. Here, the possible dispersal and establishment of Atlantic salmon are considered in Canadian Arctic fresh waters containing Arctic char (Salvelinus alpinus), an important subsistence fish species. Available information about Atlantic salmon harvests in the Canadian Arctic was summarized to assess dispersal potential. Review and synthesis of published data were used to assess the suitability of the Canadian Arctic for Atlantic salmon colonization and the interaction potential of Atlantic salmon and Arctic char in Canadian Arctic fresh waters. Establishment of Atlantic salmon in Canadian Arctic thermal habitat was deemed possible, especially with rising freshwater temperatures. Overlap in habitat preferences and life cycles of Atlantic salmon and Arctic char, along with data on resource partitioning in sympatry, implied a possibility for interaction at multiple freshwater life stages. However, many data gaps were identified that inhibit further discussion and analysis. These considerations highlight the need for further study of these two culturally, ecologically, and economically important fish species, to address growing concerns and inform future management efforts.

Summary Intestinal microbial communities from 362 anadromous Arctic char (Salvelinus alpinus) from the high Arctic Kitikmeot region, Nunavut, Canada, were characterized using high‐throughput 16S rRNA gene sequencing. The resulting bacterial communities were compared across four seasonal habitats that correspond to different stages of annual migration. Arctic char intestinal communities differed by sampling site, salinity and stages of freshwater residence. Although microbiota from fish sampled in brackish water were broadly consistent with taxa seen in other anadromous salmonids, they were enriched with putative psychrophiles, including the nonluminous gut symbiont Photobacterium iliopiscarium that was detected in >90% of intestinal samples from these waters. Microbiota from freshwater‐associated fish were less consistent with results reported for other salmonids, and highly variable, possibly reflecting winter fasting behaviour of these char. We identified microbiota links to age for those fish sampled during the autumn upriver migration, but little impact of the intestinal content and water microbiota on the intestinal community. The strongest driver of intestinal community composition was seasonal habitat, and this finding combined with identification of psychrophiles suggested that water temperature and migratory behaviour are key to understanding the relationship between Arctic char and their symbionts.

Vertebral deformities in salmonid interspecific hybrids, some of which were triploidised, were assessed across three separate year classes during the freshwater life stage. Initially, eggs from a farmed Atlantic salmon Salmo salar were crossed with the sperm from a S. salar, arctic char Salvelinus alpinus or brown trout Salmo trutta. For S. salar × S. trutta, half the eggs were triploidised. In a second- and third-year class, the eggs from a farmed S. salar were crossed with the sperm from either a S. salar or a S. trutta, and half of each group was triploidised. In the two initial-year classes, all hybrids were larger than the S. salar controls, and triploid S. salar × S. trutta were larger than diploid counterparts. In the third-year class, the S. salar × S. trutta were smaller than the S. salar, in contrast to the initial 2 year classes, although the triploid hybrids were still larger than the diploids. In the third-year class, a high degree of spontaneous triploidy was also observed in the putative diploid groups (between 16 and 39%). Vertebral deformities were consistently higher in pressure-shocked triploids than diploids, irrespective of hybridisation, but there was no consistent effect of hybridisation among experiments. Although this study was not able to explain the contrasting results for vertebral deformities between year classes, triploid S. salar × S. trutta can demonstrate impressive freshwater growth that could be of interest for future farming programmes.

Populations of Arctic char (Salvelinus alpinus) inhabiting Irish lakes are undergoing a rapid decline. In order to aid monitoring of this species in Irish lakes, a species‐specific qPCR assay was designed and subsequently tested for the detection of Arctic char's environmental DNA (eDNA) in an indoor mesocosm and in natural habitats (six lakes). Specifically, the mesocosm experiment revealed that sample volume can have significant effects on the application of eDNA approaches, whereby probability of detection depends from proximity to the source organism and volume of water filtered. When tested in the wild, positive amplification of Arctic char eDNA was observed in four of the six lakes sampled, proving that this approach can be successfully implemented in natural conditions. However, findings from the present study also showed that suboptimal sampling strategies can lead to false‐negative results (e.g., failure to detect the species when it is present). This study corroborates findings from other research on eDNA detection of fish species, showing that despite its current limitations, this approach can be a fast, noninvasive, and effective tool in aid to the conservation and management of freshwater fish species.

In this exploratory study, we studied and qualitatively evaluated a prototype video data collection system to capture and analyze fish behavior in a small-scale indoor aquaculture operation. The research objective was to design and develop a hardware / software system that would have the potential to capture meaningful data from which to extract fish size, swim trajectory, and swim velocity, ultimately as information toward an assessment of fish health. The initial work presented in this paper discusses the development choices of the prototype system, including various combinations of lighting and camera positions both inside and outside of the aquaculture tanks, and several post-processing techniques to isolate fish in video, calibrate the distance from camera to fish through water, and infer fish trajectories and swim velocities. Preliminary results provided a qualitative assessment of such a system. Specific results on the system’s ability to detect fishes’ positions, trajectories, and velocities are presently limited to observational outcomes and descriptive statistics rather than large-scale quantitative analysis. The present work lays a foundation for a future commercially hardened system that would be required for the collection of larger datasets, which would in turn facilitate the future development of machine learning (ML) algorithms to begin to statistically correlate data to fish conditions and behaviors in near-real time.

Climate change may affect temporal trends of persistent organic pollutants (POPs) in Arctic wildlife. We studied how biological and climate variables influence temporal trends of selected POP groups in landlocked Arctic char muscle and in ringed seal blubber from West and East Greenland. The variables included fish length or animal age, sex, a stable nitrogen isotope, sea ice extent, air or seawater temperature, salinity and the Arctic Oscillation Index (AOI). Model selection for multiple regression showed that the most important predictors varied among POP groups, species and region. Decreasing time trends were found for all POP groups with the exception of hexachlorobenzene (HCB) concentration which remained stable in Arctic char and ringed seals from West Greenland. When retained in the most parsimonious model, the AOI was positively associated with POP concentrations for East Greenland seals, but negatively for West Greenland seals. Seawater temperature and sea ice extent were positively associated with POP concentrations. The effects of explanatory variables on the annual rates of change in POP concentrations were relatively minor relative to the decline caused by reduction in POP emissions following national and international regulations introduced since the 1970s.

It is hypothesized that in diadromous fish, migrations may occur because of differences in the availability of food in marine and freshwater habitats. The benefits of migration to sea may be increased growth opportunities and reproductive output, while the costs may be increased mortality and increased energy use. Here we examine mortality rates of anadromous Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in fresh water and at sea over a 25-year period to test these hypotheses. Daily mortality rates were 5–15 times higher at sea than in fresh water, with highest rates for first-time migrants, inferring a clear trade-off between increased mass gain and mortality risk during the sea migration. Descending smolts were caught in a trap at the outlet of the river, individually tagged, and thereafter recorded each time they passed through the trap on their annual migration between the river and the sea. Brown trout females seemed to benefit to a higher degree from migrating to sea than did female Arctic char, probably because of the higher growth rate at sea, and hence higher reproductive output.

In present study, the analyses of essential [copper (Cu), cobalt (Co), selenium (Se) and zinc (Zn)] and non-essential elements [mercury (Hg), lead (Pb), cadmium (Cd) and arsenic (As)] in 7 fish species consumed by the indigenous people of the European Russia Arctic were conducted. The Nenets Autonomous Region, which is located in the north-eastern part of European Russia, was chosen as a Region of interest. Within it, the Nenets indigenous group (n = 6000) constitutes approximately 10% of the total population. Nearly all of the Nenets live a traditional life with fish caught in the local waters as a subsistence resource. We found that northern pike contained twice the amount of Hg compared with roach, and 3-4 times more than other fish species commonly consumed in the Russian Arctic (namely, Arctic char, pink salmon, navaga, humpback whitefish and inconnu). Fish Hg concentrations were relatively low, but comparable to those reported in other investigations that illustrate a decreasing south-to-north trend in fish Hg concentrations. In the current study, northern pike is the only species for which Hg bioaccumulated significantly. In all fish species, both Cd and Pb were present in considerably lower concentrations than Hg. The total As concentrations observed are similar to those previously published, and it is assumed to be present primarily in non-toxic organic forms. All fish tissues were rich in the essential elements Se, Cu and Zn and, dependent on the amount fish consumed, may contribute significantly to the nutritional intake by indigenous Arctic peoples. We observed large significant differences in the molar Se/Hg ratios, which ranged from 2.3 for northern pike to 71.1 for pink salmon. Values of the latter1 may increase the toxic potential of Hg, while those1 appear to enhance the protection against Hg toxicity.

In recent years, Arctic char populations in Iceland have declined and the objective of this experiment was to throw further light on these changes by examining the effect of temperature (5, 9, 13, 17, and 21 °C) on the survival, growth rate, metabolism, and physiological indices of juvenile Arctic charr (initial mean body mass 4.02 ± 0.8 g). Mortality was 60% at 21 °C while at lower temperatures it was below 5%. However, Arctic charr populations in Iceland are declining in locations where the ambient temperature is lower, suggesting that other factors may be more important in determining the abundance of the species. The optimum temperature for growth was near 14 °C. The growth rate was progressively reduced at supra-optimum temperatures with almost no growth at 21 °C. Indicators of energy reserves: condition factor, relative intestinal mass, and hepatosomatic index are all consistent with reduced feed intake at supra-optimum temperatures. The standard and maximum metabolic rate (SMR; MMR), as well as the aerobic scope for activity (AS), were maximum at 13 °C. The routine metabolic rate (RMR) increased exponentially with temperature and, at T21, it was equal to the MMR suggesting, that the RMR was limited by the MMR. Moreover, increased heart- and gill mass at 21 °C are consistent with increased stress on the cardiovascular system. These findings are in keeping with the OCLTT hypothesis that the thermal tolerance of fish is limited by the capacity of the cardiovascular system to deliver oxygen and support metabolism. Taken together, the results of this experiment suggest, that growth rate is reduced at supra-optimum temperatures because of reduced energy intake, increased metabolic demand, and limitations in the capacity of the cardiovascular system to support metabolic rate at high temperatures. At lower temperatures, growth does not appear to be limited by the AS. acceptedVersion

Fishes consume prey from across both benthic and pelagic habitats, thereby stabilizing the food webs of freshwater lakes. How fish exploit vertical and horizontal heterogeneity within the benthic environment, however, remains unclear. We characterized spatial variation in the C and N stable isotopes of a dominant benthic grazer (snails) along a water depth gradient in an oligotrophic, western Alaska lake to assess the effects of water depth on isotope characteristics in the benthic food web. Importantly, carbon stable isotopes in snails become substantially more depleted in 13C with increasing water depth. We compared this distribution of snail isotope values to those found in Arctic char (Salvelinus alpinus) diets to estimate the vertical location of char foraging on benthic resources. We found that Arctic char tended to prey on snails at greater than 10 m depth; however, individual fish specialized at a narrower range of water depths spanning from 5 to > 20 m. We used an isotope mixing model to assess the validity of using only shallow-water benthic invertebrates to represent all benthic resources in food web reconstructions and found that mixing models that only used shallow benthic prey underestimated the importance of benthic resources by about 50%. These results can help refine our understanding of how benthic prey contribute to the stability of aquatic food webs and highlight the need to account for spatial variation in the isotope composition of benthic resources in models of lake food webs.

As mercury emissions continue and climate-mediated permafrost thaw increases the burden of this contaminant in northern waters, Inuit from a Northwest passage community in the Canadian Arctic Archipelago pressed for an assessment of their subsistence catches. Sea-run salmonids (n = 537) comprising Arctic char (Salvelinus alpinus), lake trout (S. namaycush), lake whitefish (Coregonus clupeaformis), and cisco (C. autumnalis, C. sardinella) were analyzed for muscle mercury. Methylmercury is a neurotoxin and bioaccumulated with fish age, but other factors including selenium and other elements, diet and trophic level as assessed by stable isotopes of nitrogen (δ15N) and carbon (δ13C), as well as growth rate, condition, and geographic origin, also contributed depending on the species, even though all the fish shared a similar anadromous or sea-run life history. Although mean mercury concentrations for most of the species were ~0.09 µg·g−1 wet weight (ww), below the levels described in several jurisdictions for subsistence fisheries (0.2 µg·g−1 ww), 70% of lake trout were above this guideline (0.35 µg·g−1 ww), and 19% exceeded the 2.5-fold higher levels for commercial sale. We thus urge the development of consumption advisories for lake trout for the protection of pregnant women and young children and that additionally, periodic community-based monitoring be initiated.

In remote and data-limited situations such as encountered in Arctic regions, traditional ecological knowledge (TEK) is an important and valuable information source. TEK from local fishers (fishers knowledge, FK) is highly relevant to fisheries management. The integration of FK in fisheries assessments remains complicated by the lack of tools to combine scientific and FK observations. This study implements a productivity-susceptibility analysis (PSA) for assessing the risk from fishing to fish stocks and incorporate FK in the assessment process. The PSA method consists of scoring productivity attributes of fish populations and susceptibility attributes affecting fisheries exposure and intensity. The method can be adapted to incorporate FK on two levels: (1) in the validation of biological data (indirect inclusion); and (2) in the definition and scoring of independent FK attributes (direct inclusion). Risk scores measured along the productivity-susceptibility gradient serve to identify areas and populations most vulnerable to fishing activities and formulate science advice for prioritisation and management. We apply the method to small-scale fisheries for Arctic char Salvelinus alpinus in Cumberland Sound, Baffin Island, Nunavut. These fisheries are key to food security and economic growth in Canada's Arctic territories, yet management remains complicated by data paucity; by the widespread distribution and biological complexity of Arctic char stocks; and by growing uncertainties related to climate change impacts on Arctic fish and ecosystems. This paper demonstrates the usefulness of the method for combining science and FK information to improve management advice for Arctic char stocks, and applicability to other small-scale, data-limited fisheries.

Climate change has been identified as a global threat to Arctic char Salvelinus alpinus L. populations. Bayesian statistical models were used to identify important physical and ecological factors explaining Arctic char presence and persistence in Irish lakes. Maximum lake depth and the presence of mixed fish communities (i.e. including non‐salmonid fish species) were the most important drivers of Arctic char presence. There was a 75% probability that an Irish lake would contain Arctic char when maximum depth exceeded 40 m, if only a salmonid community was present. However, the required depth increased to 57 m when a mixed fish community (e.g. pike, perch or roach) was present. Similar variables explained char persistence, with surviving Arctic char populations being more likely in lakes with greater maximum depth and fewer non‐salmonid fish species. Tested temperature covariates were not important in explaining Arctic char presence or persistence in Irish lakes. A risk analysis was undertaken to identify which Arctic char lakes are vulnerable to colonisation by thermally plastic mixed fish communities due to flooding. Results indicated that 32 out of 45 lakes were not at any risk from the colonisation of thermally plastic mixed fish communities and 13 lakes had some level of risk.

Aim The Pleistocene glaciation event prompted the allopatric divergence of multiple glacial lineages of Arctic char (Salvelinus alpinus), some of which have come into secondary contact upon their recolonization of the Holarctic. While three glacial lineages (Arctic, Atlantic, and Acadian) are known to have recolonized the western Atlantic, the degree of overlap of these three lineages is largely unknown. We sought to determine the distribution of these three glacial lineages in Labrador and Newfoundland at a fine spatial scale to assess their potential for introgression and their relative contribution to local fisheries. Location Labrador and Newfoundland, Canada. Methods We sequenced a portion of the D-loop region in over 1,000 Arctic char (S. alpinus) samples from 67 locations across Labrador and Newfoundland. Results Within Labrador, the Arctic and Atlantic lineages were widespread. Two locations (one landlocked and one with access to the sea) also contained individuals of the Acadian lineage, constituting the first record of this lineage in Labrador. Atlantic and Acadian lineage individuals were found in both eastern and western Newfoundland. Multiple sampling locations in Labrador and Newfoundland contained fish of two or more different glacial lineages, implying their introgression. Glacial lineage did not appear to dictate contemporary genetic divergence between the pale and dark morph of char present in Gander Lake, Newfoundland. Both were predominately of the Atlantic lineage, suggesting the potential for their divergence in sympatry. Main conclusions Our study reveals Labrador and Newfoundland to be a unique junction of three glacial lineages which have likely hybridized extensively in this region.

In 2017, a PCR‐based survey for Piscine orthoreovirus‐3 (PRV‐3) was conducted in wild anadromous and non‐anadromous salmonids in Norway. In seatrout (anadromous Salmo trutta L.), the virus was present in 16.6% of the fish and in 15 of 21 investigated rivers. Four of 221 (1.8%) Atlantic salmon (Salmo salar L.) from three of 15 rivers were also PCR‐positive, with Ct‐values indicating low amounts of viral RNA. All anadromous Arctic char (Salvelinus alpinus L.) were PCR‐negative. Neither non‐anadromous trout (brown trout) nor landlocked salmon were PRV‐3 positive. Altogether, these findings suggest that in Norway PRV‐3 is more prevalent in the marine environment. In contrast, PRV‐3 is present in areas with intensive inland farming in continental Europe. PRV‐3 genome sequences from Norwegian seatrout grouped together with sequences from rainbow trout (Oncorhynchus mykiss Walbaum) in Norway and Coho salmon (Oncorhynchus kisutch Walbaum) in Chile. At present, the origin of the virus remains unknown. Nevertheless, the study highlights the value of safeguarding native fish by upholding natural and artificial barriers that hinder introduction and spread, on a local or national scale, of alien fish species and their pathogens. Accordingly, further investigations of freshwater reservoirs and interactions with farmed salmonids are warranted.

Anadromous Arctic char (Salvelinus alpinus) migrate back to fresh water in late summer to spawn and (or) overwinter. Upon freshwater entry, feeding is reduced or absent, and movement activity is restricted. While the physiological responses to low temperatures (e.g., growth, metabolism) are understood, specifics of the use of thermal habitat for overwintering remains poorly characterized. This study used acoustic and archival telemetry data from two lakes in southern Labrador, Canada, to study thermal habitat use during the ice-covered period. Results showed that lake-dwelling anadromous Arctic char predominantly occupied a narrow range of temperatures (0.5–2 °C) and used cooler temperatures available within the middle and upper water column. Use of the selected temperatures is likely a strategy that lowers metabolic costs and minimizes energy expenditure, preserving stored lipids for overwinter survival and the energetic costs of preparation for seaward migration. As Arctic char are visual feeders, use of the upper water column is also thought to aid foraging efficiency by increasing the likelihood of prey capture.

We compared the thermal sensitivity of oxidative muscle function between the eurythermal Atlantic salmon (Salmo salar) and the more stenothermal Arctic char (Salvelinus alpinus; which prefers cooler waters). Power output was measured in red skeletal muscle strips and myocardial trabeculae, and efficiency (net work/energy consumed) was measured for trabeculae, from cold (6°C) and warm (15°C) acclimated fish at temperatures from 2 to 26°C. The mass-specific net power produced by char red muscle was greater than in salmon, by 2-to 5-fold depending on test temperature. Net power first increased, then decreased, when the red muscle of 6°C-acclimated char was exposed to increasing temperature. Acclimation to 15°C significantly impaired mass-specific power in char (by ∼40–50%) from 2 to 15°C, but lessened its relative decrease between 15 and 26°C. In contrast, maximal net power increased, and then plateaued, with increasing temperature in salmon from both acclimation groups. Increasing test temperature resulted in a ∼3- to 5-fold increase in maximal net power produced by ventricular trabeculae in all groups, and this effect was not influenced by acclimation temperature. Nonetheless, lengthening power was higher in trabeculae from warm-acclimated char, and char trabeculae could not contract as fast as those from salmon. Finally, the efficiency of myocardial net work was approximately 2-fold greater in 15°C-acclimated salmon than char (∼15 versus 7%), and highest at 20°C in salmon. This study provides several mechanistic explanations as to their inter-specific difference in upper thermal tolerance, and potentially why southern char populations are being negatively impacted by climate change., Summary: Additional mechanistic insights indicate why Atlantic salmon are more tolerant of high temperatures than Arctic char, and why char are particularly vulnerable to climate change.

International audience; The combination of global warming and local stressors can have dramatic consequences on freshwater biota. Sediment deposition is an important pressure that can affect benthic species and benthic ontogenetic stages (eggs and larvae) habitat quality. However, knowledge on the effects of sediment in a warming context is lacking. We used a common garden approach to examine the effects of combined exposure to elevated temperature and deposited sediment on early life history traits in offspring of four wild Arctic char (Salvelinus alpinus) populations, originating from geographically isolated lakes at the southern edge of the species range. We report interactive effects of temperature and sediment, with higher temperature exacerbating the negative effects of sediments on the duration of the incubation period and on the body size – yolk expenditure trade-off during development. Our results highlight that reevaluating the impacts of sediment on organisms under the lens of global warming and at the scale of several wild populations is needed to improve our understanding of how vulnerable species can respond to environmental changes.; La combinaison du réchauffement planétaire et de facteurs de stress locaux peut avoir des conséquences dramatiques sur le biote d'eau douce. Le dépôt de sédiments exerce une importante pression qui peut avoir une incidence sur les espèces benthiques et la qualité de l'habitat de différents stades ontogénétiques (oeufs et larves) d'organismes benthiques. Les connaissances sur les effets des sédiments dans un contexte de réchauffement manquent toutefois. Nous utilisons une approche de jardin commun pour examiner les effets de l'exposition combinée à des températures accrues et à des sédiments sur des caractères des premières étapes du cycle biologique de la progéniture de quatre populations sauvages d'ombles chevaliers (Salvelinus alpinus) issus de lacs isolés géographiquement situés à la limite sud de l'aire de répartition de l'espèce. Nous faisons état d'effets interactifs de la température et des sédiments, des températures élevées exacerbant les effets négatifs des sédiments sur la durée de la période d'incubation et sur le compromis entre la taille du corps et l'utilisation du vitellus durant le développement. Nos résultats soulignent le fait qu'il est nécessaire de réévaluer les impacts des sédiments sur les organismes dans une optique du réchauffement planétaire et à l'échelle de plusieurs populations sauvages, afin d'améliorer la compréhension des réactions possibles d'espèces vulnérables aux changements environnementaux. [Traduit par la Rédaction]

High levels of organochlorines (OCs) have been measured in arctic char (Salvelinus alpinus) from Lake Ellasjøen on Bjørnøya, Norway (74.30°N, 19.0°E). In a nearby lake, Laksvatn, the OC-levels in arctic char were low. A previous study has shown that char from Ellasjøen had significantly higher levels of DNA double strand breaks (DSBs) than char from Lake Laksvatn. Even though there is increasing evidence of the genotoxic effects of OCs, little is known about the effects of OCs on the DNA repair system. The aim of the present study was to determine if the two main DNA DSB repair mechanisms, homologous recombination (HR) and non-homologous end-joining (NHEJ), are affected by the higher OC and DSB level in char from Ellasjøen. This was analysed by comparing the transcript level of 11 genes involved in DNA DSB repair in char liver samples from Ellasjøen (n = 9) with char from Laksvatn (n = 12). Six of the investigated genes were significantly upregulated in char from Ellasjøen. As the expression of DNA DSB repair genes was increased in the contaminant-exposed char, it is likely that the DNA DSB repair capacity is induced in these individuals. This induction was positively correlated with the DNA DSB and negatively correlated with one or several OCs for four of these genes. However, the strongest predictor variable for DNA repair genes was habitat, indicating genetic differences in repair capacity between populations. As char from Ellasjøen still had significantly higher levels of DSBs compared to char from Laksvatn, it is possible that chronic exposure to OCs and continued production of DSB has caused selective pressure within the population for fixation of adaptive alleles. It is also possible that DSB production was exceeding the repair capacity given the prevailing conditions, or that the OC or DSB level was above the threshold value of inhibition of the DNA repair system resulting in the rate of DNA damage exceeding the rate of repair. © 2020 Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

This ethnographic study explores and compares the relationships that locals in Rossfjord, North Norway, have to the oystercatcher and the sea-going Arctic char respectively. Both these animals are highly valued locally, while the valuations at first look very different. The oystercatcher is protected by building bin-cases for its nesting, while the Arctic char is killed and eaten. Discussing these valuations against the value theory of David Graeber, I argue that they both connect to an underlying perception of the freedom and autonomy of wild animals, where what is not fully understood enhances an experience of wonder and appreciation of what I call the wild.

My experiences during my first visit to the Arctic challenged my preconceptions and opened my eyes to some of the realities of arctic research. What I thought was going to be a harsh environment and challenging culture to fit into, turned out to be a magical landscape and people filled with warmth and welcome. In this chapter, I discuss some of the fears and uncertainties I had before traveling to the Arctic, navigating being a vegan in a culture whose food system centres around animals, and designing a research project with the community.

Skeletal deformities and ocular cataracts have limited the farm performance of sterile triploid salmonids, but have not been assessed in Arctic char (Salvelinus alpinus). We repeatedly radiographed mixed-sex diploid and triploid char (n = 110/ploidy) of Hammerfest (Norway) origin reared on a natural photoperiod and temperature in freshwater over a 3-year period and assessed cataracts at termination. At the population level, triploids were significantly (p < 0.001) heavier at tagging, but lighter at harvest (mass (g) ± SE; tagging, 48 ± 2 vs 67 ± 3; harvest, 2015 ± 83 vs 1639 ± 71, in diploids and triploids, respectively). These growth differences were mainly related to sex and life history, as immature fish were generally smaller than those that matured, and triploids showed lower levels of sexual maturation throughout (mature (%); diploid males, 20 and 65; diploid females, 12 and 83; triploid males, 2 and 40; triploid females 0 and 0, after 2 and 3 years, respectively). In addition, males grew quicker than females, irrespective of ploidy. When comparing fish of the same sex and life history, there was no significant growth disadvantage of triploidy. However, survival was significantly lower in triploids (p < 0.001: 94 vs 86% from tagging to harvest in diploids and triploids, respectively) and they had a significantly higher incidence of fish with one or more deformed vertebra throughout (p < 0.001, 99 vs 71% in 3 year-old diploid and triploids, respectively). Cataract prevalence was high (>90% in both ploidy), but severity was low (on average, 0.1). Based on the average wet body mass of immature fish and losses due to sexual maturation and mortality, mono-sex stocks of male triploid fish gave the highest return per 100 juveniles stocked, followed by diploid males, diploid females, and triploid females (87.5, 83.0, 80.8, and 69.3 kg, respectively) at the earliest opportunity to harvest (i.e. when the fish first reached 0.7–1.0 kg). Therefore, all-male triploids may provide benefits to char aquaculture although their skeletal health should be addressed.

RATIONALE: Dried blood spots (DBSs) are gaining popularity for biomarker analyses in ecological research due to their advantages for use in field-based research and in remote settings, however, many DBS biomarkers remain unvalidated. We validated the application of compound-specific stable nitrogen isotope analyses of amino acids (CSIA-AAs) to field-prepared DBSs for determining trophic positions of wild-caught Arctic char (Salvelinus alpinus). METHODS: Whole blood and muscle from Arctic char were collected and DBSs were created in the field. We measured the stable nitrogen isotope ratios (expressed as δ(15)N values) of the amino acids glutamic acid (Glu) and phenylalanine (Phe) isolated from Arctic char samples using CSIA-AAs. We then compared amino acid δ(15)N values from DBSs and the other sample types (whole blood and muscle) from the same specimens. We calculated and compared trophic position estimates generated from whole blood, DBSs, and muscle. RESULTS: The δ(15)N values of Glu and Phe, as well as trophic position estimates from DBSs were highly correlated with δ(15)N values and estimates from both whole blood and muscle. DBS amino acid δ(15)N values and trophic position estimates agreed well with those from whole blood. Although, mean differences between amino acid δ(15)N values from DBSs and muscle were noted, the offsets were small and resulted in a 0.2 mean difference between trophic position estimates for DBSs and muscle. CONCLUSIONS: We demonstrate that the application of CSIA-AAs to field-prepared DBSs of Arctic char generates similar trophic position estimates compared to whole blood and muscle. We suggest that DBSs could be developed as a minimally invasive sampling technique to study feeding ecology of wild fish and perhaps other organisms of interest.

The identification of food fish bearing anthropogenic contaminants is one of many priorities for Indigenous peoples living in the Arctic. Mercury (Hg), arsenic (As), and persistent organic pollutants including polychlorinated biphenyls (PCBs) are of concern, and these are reported, in some cases for the first time, for fish sampled in and around King William Island, located in Nunavut, Canada. More than 500 salmonids, comprising Arctic char, lake trout, lake whitefish, and ciscoes, were assayed for contaminants. The studied species are anadromous, migrating to the ocean to feed in the summers and returning to freshwater before sea ice formation in the autumn. Assessments of muscle Hg levels in salmonids from fishing sites on King William Island showed generally higher levels than from mainland sites, with mean concentrations generally below guidelines, except for lake trout. In contrast, mainland fish showed higher means for As, including non-toxic arsenobetaine, than island fish. Lake trout were highest in As and PCB levels, with salmonid PCB congener analysis showing signatures consistent with the legacy of cold-war distant early warning stations. After DNA-profiling, only 4&ndash, 32 Arctic char single nucleotide polymorphisms were needed for successful population assignment. These results support our objective to demonstrate that genomic tools could facilitate efficient and cost-effective cluster assignment for contaminant analysis during ocean residency. We further suggest that routine pollutant testing during the current period of dramatic climate change would be helpful to safeguard the wellbeing of Inuit who depend on these fish as a staple input to their diet. Moreover, this strategy should be applicable elsewhere.

This work presents Arctic Char Algorithm (ACA) for solving optimal reactive power problem. In North America movement of Arctic char phenomenon is one among the twelve-monthly innate actions. Deeds of Arctic char have been imitated to design the algorithm. In stochastic mode solutions are initialized with one segment on every side of to the route ascendancy; particularly in between lower bound and upper bounds. Previous to the movement, Arctic char come to a decision about the passageway based on their perception. This implies stochastic mix up of control parameters to push the Arctic char groups (preliminary solution) in mutual pathway (evolutionary operators). Projected Arctic Char Algorithm (ACA) has been tested in standard IEEE 14,300 bus test system and simulation results show the projected algorithm reduced the real power loss extensively.

Diet, age, and growth rate influences on fish mercury concentrations were investigated for Arctic char (Salvelinus alpinus) and brook trout (Salvelinus fontinalis) in lakes of the eastern Canadian Arctic. We hypothesized that faster-growing fish have lower mercury concentrations because of growth dilution, a process whereby more efficient growth dilutes a fish’s mercury burden. Using datasets of 57 brook trout and 133 Arctic char, linear regression modelling showed fish age and diet indices were the dominant explanatory variables of muscle mercury concentrations for both species. Faster-growing fish (based on length-at-age) fed at a higher trophic position, and as a result, their mercury concentrations were not lower than slower-growing fish. Muscle RNA/DNA ratios were used as a physiological indicator of short-term growth rate (days to weeks). Slower growth of Arctic char, inferred from RNA/DNA ratios, was found in winter versus summer and in polar desert versus tundra lakes, but RNA/DNA ratio was (at best) a weak predictor of fish mercury concentration. Net effects of diet and age on mercury concentration were greater than any potential offset by biomass dilution in faster-growing fish. In these resource-poor Arctic lakes, faster growth was associated with feeding at a higher trophic position, likely due to greater caloric (and mercury) intake, rather than growth efficiency.

Distinguishing neutral and adaptive genetic variation is one of the main challenges in investigating processes shaping population structure in the wild, and landscape genomics can help identify signatures of adaptation to contrasting environments. Arctic Char (Salvelinus alpinus) is an anadromous salmonid and the most harvested fish species by Inuit people, particularly so in Nunavik (Canada), one of the most recently deglaciated region in the world. Unlike most other anadromous salmonids, Arctic Char occupy coastal habitats near their overwintering rivers during their marine phase. The main objective of this study was to document the putative neutral and adaptive genomic variation of anadromous Arctic Char populations in Nunavik (Québec, Canada) and bordering regions. A second objective was to interpret our results in the context of fisheries management in Nunavik. We used genotyping-by-sequencing (GBS) to genotype 18,112 filtered single nucleotide polymorphisms (SNPs) for 650 individuals sampled in 23 locations (average sample size per location = 28) along >2,000 km of coastline. Our results reveal a hierarchical genetic structure, whereby neighboring hydrographic systems harbour distinct populations grouping within major oceanographic basins, namely the Hudson Bay, Hudson Strait, Ungava Bay and Labrador Sea. We found genetic diversity and differentiation to be consistent with both the expected post-glacial recolonization history and patterns of isolation-by-distance reflecting contemporary gene flow. Furthermore, using three gene-environment association (GEA) methods we found genomic evidence for local adaptation to freshwater and marine environmental components, especially in relation to sea-surface and air temperatures during summer, as well as salinity. Our results support fisheries management at a regional level, and other implications on hatchery projects and adaptation to climate change are discussed.

Dried blood spots (DBS), created by applying and drying a whole blood sample onto filter paper, provide a simple and minimally invasive procedure for collecting, transporting, and storing blood. Because DBS are ideal for use in field and resource-limited settings, we aimed to develop a simple and accurate DBS-based approach for assessing mercury (Hg) exposure and dietary carbon sources for landlocked Arctic char, a sentinel fish species in the Arctic. We collected liquid whole blood (from the caudal vein), muscle, liver, and brains of Arctic char (n = 36) from 8 lakes spanning a Hg gradient in the Canadian High Arctic. We measured total Hg concentrations ([THg]) of field-prepared DBS and Arctic char tissues. Across a considerable range, [THg] of DBS (0.04-3.38 μg/g wet wt) were highly correlated with [THg] of all tissues (r2 range = 0.928-0.996). We also analyzed the compound-specific carbon isotope ratios (expressed as δ13 C values) of essential amino acids (EAAs) isolated from DBS, liquid whole blood, and muscle. The δ13 C values of 5 EAAs (δ13 CEAAs ; isoleucine [Ile], leucine [Leu], phenylalanine [Phe], valine [Val], and threonine [Thr]) from DBS were highly correlated with δ13 CEAAs of liquid whole blood (r2 range = 0.693-0.895) and muscle (r2 range = 0.642-0.881). The patterns of δ13 CEAAs of landlocked Arctic char were remarkably consistent across sample types and indicate that EAAs are most likely of algal origin. Because a small volume of blood (~50 µL) dried on filter paper can be used to determine Hg exposure levels of various tissues and to fingerprint carbon sources, DBS sampling may decrease the burdens of research and may be developed as a nonlethal sampling technique. Environ Toxicol Chem 2020;39:893-903. © 2020 SETAC.

The Arctic climate is changing rapidly, yet predicting how aquatic species will respond to these changes remains challenging given the lack of empirical data for most high-latitude taxa. Acoustic telemetry has recently emerged as an important methodology for understanding horizontal and vertical space-use patterns in fishes. Here, we used acoustic telemetry to document marine habitat use and depth/temperature preference of 26 anadromous Arctic char Salvelinus alpinus within the Kitikmeot Sea region of the Canadian central Arctic over 4 yr (2013- 2016). Most detections (~70%) were within the top 3 m of the water column, and most were in estuarine (72.6%) vs. marine (27.4%) habitats. Arctic char preferred deeper waters later in the summer, but the temperature they occupied remained relatively constant throughout the marine feeding season (~5-8°C). Most Arctic char exhibited some degree of repetitive diving behavior, with individuals diving to 35 m. Diving activity increased later in the summer marine feeding season and is likely a response to the seasonal transition of their preferred prey to deeper waters as the season progresses. Finally, Arctic char preferred deeper waters with less ice cover and during the day, the latter suggesting potential diel patterns to marine habitat use. Finally, year-to-year variation in Arctic char depth and temperature use was very modest despite differences in climatic and ice conditions. This result suggests that habitat use is relatively fixed and may reflect their thermal and osmoregulatory physiology, which has important implications for forecasting the impacts of a changing Arctic on this economically valuable species.