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Land acknowledgments in the Arctic must reflect continuing practices such as hunting marine mammals and the deep physical and spiritual relationships that Arctic Indigenous Peoples have with the world around them. Land acknowledgments - statements about the Indige-nous Peoples on whose lands others live and work - have become increasingly common in Australia, Canada, the United States, and elsewhere. [Extracted from the article]

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. [ABSTRACT FROM AUTHOR]

Conceptual models of adaptive divergence and ecological speciation in sympatry predict differential resource use, phenotype–environment correlations, and reduced gene flow among diverging phenotypes. While these predictions have been assessed in past studies, connections among them have rarely been assessed collectively. We examined relationships among phenotypic, ecological, and genetic variation in Arctic charr (Salvelinus alpinus) from six Icelandic localities that have undergone varying degrees of divergence into sympatric benthic and pelagic morphs. We characterized morphological variation with geometric morphometrics, tested for differential resource use between morphs using stable isotopes, and inferred the amount of gene flow from single nucleotide polymorphisms. Analysis of stable isotopic signatures indicated that sympatric morphs showed similar difference in resource use across populations, likely arising from the common utilization of niche space within each population. Carbon isotopic signature was also a significant predictor of individual variation in body shape and size, suggesting that variation in benthic and pelagic resource use is associated with phenotypic variation. The estimated percentage of hybrids between sympatric morphs varied across populations (from 0% to 15.6%) but the majority of fish had genotypes (ancestry coefficients) characteristic of pure morphs. Despite evidence of reduced gene flow between sympatric morphs, we did not detect the expected negative relationship between divergence in resource use and gene flow. Three lakes showed the expected pattern, but morphs in the fourth showed no detectable hybridization and had relatively low differences in resource use between them. This coupled with the finding that resource use and genetic differentiation had differential effects on body shape variation across populations suggests that reproductive isolation maintains phenotypic divergence between benthic and pelagic morphs when the effects of resource use are relatively low. Our ability to assess relationships between phenotype, ecology, and genetics deepens our understanding of the processes underlying adaptive divergence in sympatry. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The Arctic charr breeding programme has been a main driving force for developing the aquaculture industry in Sweden. Selection has been performed for almost 40 years using animals from a closed breeding nucleus. The aim of the current study was to evaluate the potential of further improving growth‐related traits taking into account the existence of genotype‐by‐environment interaction. Furthermore, we investigated the magnitude of the genetic component associated with survival to the eyed stage and potential associations with inbreeding coefficients. A preliminary heritability estimate of 0.23 (SE 0.20) was obtained for survival to the eyed stage using records spanning from 2000 to 2017 (n = 230). Moreover, moderate‐to‐high heritability estimates (0.27–0.49) were obtained for growth‐related traits (body weight and length), using animals from the latest generation of selection (year class 2017). Those animals (n = 2,776), originating from 55 full‐sib families, were split into two groups and reared in separate land‐based facilities of commercial fish farms in Sweden. The growth‐related traits were recorded twice in both sites when animals were of >1 and >2 years of age. Existence of sexual growth dimorphism was indicated with the males having on average 6%–8% higher total length and 22%–34% higher body weight. Furthermore, high genetic correlations regarding growth traits were obtained amongst animals reared at the two different sites (0.82–0.95). In addition, we assessed the accuracy of best linear unbiased prediction (BLUP)‐derived estimated breeding values (EBVs) when phenotypes from each rearing site were subsequently masked and used as a validation set. A mean prediction accuracy of 0.60 (length) and 0.64 (weight) were derived for both rearing sites. Overall, our results suggest that further growth improvements should be possible in the subsequent generations of selection. Finally, even though indications for the existence of an underlying genetic component(s) involved in survival to the eyed stage were obtained additional data will be required for elucidating its magnitude. [ABSTRACT FROM AUTHOR]

Divergent selection is a powerful driver of speciation and has been widely studied in relation to the physical characters of organisms. Behavioural traits also significantly contribute to the evolutionary processes of divergence. However, studying such effects is fraught with difficulties as the development of behavioural traits is likely to be complex and is moulded by ontogenetic processes such as shifts in habitat use. Here we explored how several aspects of juvenile behavioural variation may relate to adaptive divergence in a freshwater fish. We assessed whether and how juveniles of two recently evolved, sympatric morphs of Arctic charr, Salvelinus alpinus , a small benthivorous and a planktivorous charr, show genetically based differences in personality that conform to their respective ecological niches, and whether these differences could contribute to reproductive isolation by generating maladaptive hybrid behaviours. Studying three aspects of behavioural variation (average trait value, consistent individual differences and trait correlations), we assessed the sociality and risk-taking propensity of hybrids and pure-morph offspring reared in common conditions. While no difference in average behavioural responses could be observed, the hybrids tended to show less repeatable behaviours and were not intermediate for behavioural syndromes that appear to differ between the two morphs. These results provide limited evidence of personality trait divergence among polymorphic fish, and suggest subtle, nonadditive effects of hybridization on the development of such traits. • Average personality traits differences between charr morphs were not observed. • Trait correlations appear to differ between morphs. • Consistent individual differences tended to be altered in their hybrids. • Intermediate trait correlations were not observed in the hybrids. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Carotenoid pigmentation in Salvelinus alpinus has been connected to stress responsiveness in earlier studies. This has, however, only been tested with time‐consuming image analysis from photos. Here, we used quick visual categorization of carotenoid pigmentation to investigate the stress responsiveness of the extreme groups. The visually selected charr were then exposed to a net restraint stressor. Arctic charr with few spots also had a lower stress responsiveness compared to charr with many spots. Thus, visual selection could be used as a simple method within aquaculture. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The introduced monogenean Gyrodactylus salaris (Malmberg, 1957) is categorized as one of the most severe threats against Atlantic salmon (Salmo salar Linnaeus, 1758) in Norway and has almost eradicated salmon populations in the Skibotn and Signaldalen Rivers in northern Norway. The parasite was unintentionally introduced to the Skibotn River in 1976 via release of infested Atlantic salmon smolt from Sweden. The parasite is restricted to freshwater, and survives at most a few days without its host. Therefore, eradication of all hosts in the infected river systems has been the preferred strategy to eliminate the parasite. After two failed eradication attempts in 1988 and 1995, the parasite spread further to neighbouring rivers. This, along with several other failed rotenone treatments in Norway in the 1990s, resulted in severe criticism of the national eradication strategy for G. salaris. Still, the eradication program continued, and the failed eradication attempts were analysed for possible improvements. Arctic char (Salvelinus alpinus, Linnaeus, 1758) has proved to be a potential long-term host for the parasite and infested char were documented to have survived in small, groundwater-fed tributaries and ponds during the first two eradication attempts in the Skibotn River. Low limits on allowed rotenone concentrations set by the pollution control authorities might also have contributed to the failures. A third attempt at eradicating the parasite from River Skibotnelva was made in 2015 and 2016, using new knowledge about the parasite and its hosts, renewed strategies to map and deal with dilution from groundwater intrusion and an official acceptance of increased concentrations of rotenone. Treatments for two consecutive years was the main strategy improvement from previous eradication attempts. Water samples showed sufficient levels of rotenone concentrations at all sample points during the treatment periods. Significant efforts in collecting all possible surviving fish from the first-year treatment and screening them for G. salaris revealed no surviving parasites at the time of the second-year treatment. The national G. salaris eradication campaign includes a surveillance programme for eradication confirmation. The results so far are positive for the Skibotn Region, but the earliest an eradication confirmation can be issued earliest is 2021. [ABSTRACT FROM AUTHOR]

Northern form Dolly Varden is an anadromous char with significant ecological value found in high-gradient rivers of the Western Arctic. Because of declines in population abundance, Dolly Varden was recently designated as "Special Concern" under the federal Species at Risk Act. This species is also of great cultural and dietary significance to Indigenous Peoples of many communities in the Western Arctic; thus, expanding knowledge of the distribution, biology, and essential habitat is an important priority. We present results of a fisheries survey in the headwaters of the Arctic Red River, Northwest Territories, that focused on confirming the presence of Dolly Varden. Of 143 fish captured among 12 sampling locations, two were Arctic grayling (Thymallus arcticus), 33 were slimy sculpin (Cottus cognatus), and 108 were char identified using qualitative and quantitative morphological features. A subsample of 44 char voucher specimens were frozen whole and later identified using a linear discriminant function (LDF) based on meristic counts and morphological measurements, and a mitochondrial DNA genetic marker. LDF scores indicated that char collected in the Arctic Red River were northern form Dolly Varden. Genetic analysis showed that all but one char possessed mitochondrial DNA sequences common in northern form Dolly Varden from Canada. Our results confirm the presence of Dolly Varden in the Arctic Red River headwaters, extending the confirmed known distribution of this taxon in the Northwest Territories approximately 450 km south and 100 km east of previously delimited areas. [ABSTRACT FROM AUTHOR]

Currently, no information is available on the effect of progressively decreasing temperatures on the sensory quality of Arctic charr. The objective of this study was to investigate if and how different and progressively changing rearing temperatures affect the sensory quality of cooked and raw fillets of Arctic charr. The effects of rearing temperature on the sensory quality of Arctic charr (weight range 622–888 g) were investigated. Rearing temperature was changed during the experimental period as the fish were reared at constant or decreased temperature during October to April and subsequently reared at two constant temperatures from April to August establishing six different rearing temperature combinations. Significant differences were seen in all four main sensory attributes groups, that is odour, appearance, flavour and texture. Freshness characteristics such as sweet odour and flavour, and metallic odour and flavour increased with decreasing rearing temperature, whereas musty odour and flavour decreased. Rearing temperature had a clear effect on the colour of the fillets. Lower rearing temperature increased colour intensity substantially. Softness, juiciness and tenderness increased with decreased rearing temperature. A trend was seen towards more effect from final rearing temperature than initial temperature on the sensory attributes studied. Spoilage characteristics, that is, sour and rancid odour and flavour, and off‐odour and flavour were either very weak or not noticeable in all sample groups. [ABSTRACT FROM AUTHOR]

Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels. [ABSTRACT FROM AUTHOR]

Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self‐sustaining population that has adapted to the unique conditions of the sub‐Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size‐dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub‐Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub‐Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub‐Arctic lakes. Although they inhabit a resource‐poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large‐scale environmental change as represented by climate change. [ABSTRACT FROM AUTHOR]

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 δ15N values) of the amino acids glutamic acid (Glu) and phenylalanine (Phe) isolated from Arctic char samples using CSIA‐AAs. We then compared amino acid δ15N 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 δ15N values of Glu and Phe, as well as trophic position estimates from DBSs, were highly correlated with δ15N values and estimates from both whole blood and muscle. The DBS amino acid δ15N values and trophic position estimates agreed well with those from whole blood. Although mean differences between amino acid δ15N 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 to those from 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. [ABSTRACT FROM AUTHOR]

Reliable age estimation of anadromous Arctic Char, Salvelinus alpinus, is important for assessment and management of populations. We examined precision (coefficient of variation-CV% and percent agreement) and bias of within-reader age estimates between whole and thinsection, and whole and grind otolith preparation methods based on single reads using samples from two populations of Arctic Char (Tatik Lake and Hornaday River, Northwest Territories) collected between 2010 and 2012. Additionally, standardized criteria were used to assess between-method differences in age reader confidence to determine whether perceived improvement in confidence resulted in different age estimates. Whole vs thin-section CV was 4.6% while exact percent agreement was 51-56%. Bias between whole and thin-section methods was evident among older age classes where the whole method tended to underestimate compared to thin-sectioning. A combination of whole and thin-section otolith preparation methods is recommended to minimize sample preparation time while maintaining confidence in age estimates. The age estimation protocol for Tatik Lake and Hornaday River would use the whole method for = age-12 and = age-9, respectively and use the thin-section method thereafter. Any otolith, regardless of age, would be thin-sectioned if the confidence associated with the whole read was low as thin-sectioning produced a greater frequency of high-confidence age estimates compared to whole. While age estimates from whole otoliths read with low confidence were not significantly different when thin-sectioned and read with high confidence, thin-sectioning improved reader confidence for 50.5-58.4% of the whole reads with low confidence. Similar findings were observed between whole and grind otolith preparation methods. Finally, we evaluated bias between the whole method (used historically by one age reader) and the combination of whole and thin-section method (used recently by another age reader), to assess the comparability of historical and contemporary age data. Between-reader CV was 6.0% for Tatik Lake and 6.7% for Hornaday River, while exact percent agreement was 45% and 54%, respectively. The contemporary method tended to produce older age estimates resulting in differences in age frequency distributions, maximum age, and annual mortality estimates. However, there was no significant difference in von Bertalanffy growth parameters for either location. Researchers should consider the implication of these differences when working with both historic and contemporary data sets for these locations and any others with a similar difference in the methods used to assign age estimates. [ABSTRACT FROM AUTHOR]

Arctic Char, Salvelinus alpinus, are frequently exploited in the Halokvik and Jayko rivers by Cambridge Bay fishers for subsistence and commercial purposes. Commercial fisheries for anadromous Arctic Char in the Halokvik River date back to 1968 and at the Jayko River the commercial fishery began in 1975; both have been subjected to periodic closures throughout their history. Harvest data are available for both systems and each has a long-time series of fishery-dependent data. Fishery-independent data are limited for both waterbodies. Through collaboration with the Ekaluktutiak Hunters and Trappers Organization (EHTO), Fisheries and Oceans Canada (DFO) developed the Cambridge Bay Arctic Char Integrated Fisheries Management Plan (IFMP) to promote a common understanding of the "basic rule" for the sustainable management of arctic fisheries. To assess the sustainability of these stocks and to further our understanding of commercial harvest on stock persistence, we applied depletionbased stock reduction analysis (DB-SRA) and other data limited models to assess Arctic Char status and formulate sustainable fisheries management options. Our data indicate that commercial fishery harvests in both rivers underwent significant inter-annual variation. Growth in standard length and round weight of anadromous Arctic Char differed with year, river and sex. Male fish had 16% higher L8 and 18% lower k values than females in the Halokvik River while male char had 4% higher L8 and 9% higher k at the Jayko River. In terms of empirical relationships between natural mortality and somatic growth parameters, M was estimated to be 0.1485 ± 0.1272 per year and 0.1758 ± 0.0372 per year at the Halokvik and Jayko rivers, respectively. Using the DB-SRA model, the mean and standard error values of virgin biomass (K) were estimated to be 104.99 ± 0.55 t and 167.15 ± 0.58 t in the Halokvik and Jayko rivers, respectively. Arctic Char in the Halokvik River appeared healthy before 1988 and the population appears to have been overfished since then. Fishing pressure was acceptable until 2004 and the fisheries showed a five-year period of overexploitation during 2005-2010. Currently, the population is still in the overfished state. In the Jayko River, a healthy state was sustained until 1992. Since then, the population has been in an overfished state as F increased. In particular, since 2012, the population has been overfished as the fishery is in a state of moderate overexploitation. Both fisheries have experienced overfishing as determined by the assessment. [ABSTRACT FROM AUTHOR]

Data collected from a fishery-dependent monitoring program between 1992 and 2015 and supplemental information collected in 1978 and 1987 were used to inform a population assessment of anadromous Arctic Char (Salvelinus alpinus) from the Kuujjua River, Northwest Territories. The stock is important for the subsistence and economy of residents from the hamlet of Ulukhaktok in the Inuvialuit Settlement Region. Arctic Char from the Kuujjua River stock are harvested during summer when feeding along the coast in a mixed-stock fishery, and during winter (under-ice) while overwintering in Tatik Lake. The monitoring program conducted during the winter fishery employed subsistence fishers from Ulukhaktok to collect harvest, catch-effort, and biological data for the majority of the duration of the fishery. Catch-effort in Tatik Lake varied without trend although the frequency of relatively high values (> 125 Arctic Char/100 m/24 hours) increased from 2006 to 2015. The biological data reveal the winter fishery harvests Arctic Char mainly between 500 and 700 mm, 1,000 and 3,500 g, and 8 and 12 years of age. Mean length and weight increased from 533 to 633 mm and 1,893 to 3,354 g, respectively, between 2008 and 2012, and have been relatively stable through 2015. Mean age increased from 8.3 to 10.3 years between 2010 and 2012 and was then stable through 2015 with the consistent presence of fish = 15 years of age. The von Bertalanffy growth parameters of Arctic Char from Tatik Lake were L∞= 703, K= 0.42, and t0= 2.61, with no statistically significant difference between sexes. The mean length of fish 9 to 12 years of age increased beginning in 2008 and continued through 2015. Over the time-series, mean length and weight, and length-atage followed a quasi-cyclic pattern. Condition factor remained relatively high (K = 1.2) and stable from 2008 to 2015, which suggests feeding opportunities were favorable for growth during this period. The annual mortality rate between 2011 and 2015 was stable (~ 30%). Where comparisons were possible, some similarities were observed between the biological data collected from the 1992-2015 monitoring, and data collected from this same fishery in 1978 and 1987. Collectively, the catch and monitoring data through 2015 indicate that the Kuujjua River population is not experiencing overfishing and the current stock status is healthy. [ABSTRACT FROM AUTHOR]

Salmon farming has multiplied from a side business of coastal farmers to one of the world's major aquaculture species. This has dramatically altered the disease dynamics between farmed and wild salmonids. As salmon fish farming has increased, new restrictions have been enforced to combat emerging density-dependent impacts of pathogen spillover. In most northern and arctic regions, the effects of pathogens from fish farms on wild salmonids have been minimal for two key reasons: (i) relative low density of fish farms in the north and (ii) cold water temperatures. However, both factors are set to change dramatically. On one side, there is an increasing interest in utilizing northern areas for fish farming due to limited capacity for expansion in mid-latitude regions. On the other side, climate change is rapidly changing these northern ecosystems. High-latitude regions inhabit some of the largest remaining wild Atlantic salmon populations in the world along with sea trout and Arctic charr. Wild salmonids in the north have most likely seldom been exposed to high infection pressure, and we question how these populations will cope with changes that are coming. We identify 12 research questions emerging from these imminent changes and discuss methodologies for addressing them. We conclude that policies related to fish farming must consider uncertainties with respect to pathogen dynamics in the north until these research questions are fully addressed. [ABSTRACT FROM AUTHOR]

Interspecific hybridization has been observed between several fall-spawning salmonids (e.g., chum salmon × pink salmon, southern Asian Dolly Varden × white-spotted charr, and masu salmon × white-spotted charr: Yamamoto et al. [18]; Ichimura et al. [6]; Fukui [2]). Rainbow trout ( I Oncorhynchus mykiss i ) is another non-native species that has become widely established in Japan; however, because rainbow trout spawn mainly in spring (rarely in autumn or winter: Kitano et al. [8]), no instances of hybridization with a native salmonid species have been reported so far. During the 2021 spring survey, four mature male charr (118-191 mm FL) were captured from 116 charr on 8 April 2021 in an upper reach of the Horonai River. [Extracted from the article]

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. [ABSTRACT FROM AUTHOR]

The genetic underpinnings of incipient speciation, including the genomic mechanisms which contribute to morphological and ecological differentiation and reproductive isolation, remain poorly understood. The repeated evolution of consistently, phenotypically distinct morphs of Arctic Charr (Salvelinus alpinus) within the Quaternary period offer an ideal model to study the repeatability of evolution at the genomic level. Sympatric morphs of Arctic Charr are found across this species' circumpolar distribution. However, the specific genetic mechanisms driving this morph differentiation are largely unknown despite the cultural and economic importance of the anadromous morph. We used a newly designed 87k SNP chip to investigate the character and consistency of the genomic differences among sympatric morphs within three recently deglaciated and geographically proximate lakes in Labrador, Canada. We found genetically distinct small and large morph Arctic Charr in all three lakes consistent with resident and anadromous morphs, respectively. A degree of reproductive isolation among sympatric morphs is likely given genome‐wide distributions of outlier SNPs and high genome‐wide FSTs. Across all lakes, outlier SNPs were largely nonoverlapping suggesting a lack of genetic parallelism driving morph differentiation. Alternatively, several genes and paralogous copies of the same gene consistently differentiated morphs across multiple lakes suggesting their importance to the manifestation of morphs. Our results confirm the utility of Arctic Charr as a model for investigating the predictability of evolution and support the importance of both genetic parallelism and nonparallelism to the incipient speciation of Arctic Charr morphs. [ABSTRACT FROM AUTHOR]

As the global climate warms, the fate of lacustrine fish is of huge concern, especially given their sensitivity as ectotherms to changes in water temperature. The Arctic charr (Salvelinus alpinus L.) is a salmonid with a Holarctic distribution, with peripheral populations persisting at temperate latitudes, where it is found only in sufficiently cold, deep lakes. Thus, warmer temperatures in these habitats particularly during early life stages could have catastrophic consequences on population dynamics. Here, we combined lake temperature observations, a 1-D hydrodynamic model, and a multi-decadal climate reanalysis to show coherence in warming winter water temperatures in four European charr lakes near the southernmost limit of the species' distribution. Current maximum and mean winter temperatures are on average ~ 1 °C warmer compared to early the 1980s, and temperatures of 8.5 °C, adverse for high charr egg survival, have frequently been exceeded in recent winters. Simulations of winter lake temperatures toward century-end showed that these warming trends will continue, with further increases of 3–4 °C projected. An additional 324 total accumulated degree-days during winter is projected on average across lakes, which could impair egg quality and viability. We suggest that the perpetuating winter warming trends shown here will imperil the future status of these lakes as charr refugia and generally do not augur well for the fate of coldwater-adapted lake fish in a warming climate. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Arctic Char (Salvelinus alpinus), both anadromous (sea run) and landlocked, are an important traditional food source for residents of Paulatuk, a community within the Inuvialuit Settlement Region of the Northwest Territories. Voluntary community-based harvest surveys were conducted monthly in Paulatuk, between 2003 and 2013, to enumerate fish and marine mammal subsistence harvest. These surveys build on historical subsistence, sport, and commercial fisheries records. Data from these surveys were examined with a focus on the seasonality and location of Arctic Char subsistence harvest. Total anadromous Arctic Char catches peaked in 1982 (5,456 fish) during the period when a commercial fishery operated (1968-1986). Subsistence harvest varied between 479 fish in 2008 and 1,793 fish in 2009, with an average of 1,228 fish over the time period (2003-2013). Summer (June-September) harvests were highest from the coastal area near the mouth of the Hornaday River, although there appeared to be a trend towards increasing harvests at the Lasard Creek area. Landlocked Arctic Char harvest occurred predominantly during spring (May and June); it was lower and more variable than anadromous Arctic Char harvest. Winter (October-December) fisheries primarily targeted anadromous Arctic Char in the upper Hornaday River. In 1998 the Paulatuk Char Working Group led the implementation of community-based management and monitoring measures that included a voluntary anadromous Arctic Char subsistence harvest level. These measures continue to support sustainable management of Arctic Char populations in the area. [ABSTRACT FROM AUTHOR]

Consistent individual differences in behavior have been demonstrated for many animals, but there are few studies of consequences of such repeated behavior in the wild. We tested consistency in migration timing to and from the sea among anadromous Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta), using data from a study period of about 25 years, including more than 27,000 uniquely Carlin‐tagged individuals that migrated to sea for feeding in the spring and returned to the river in late summer for up to 13 successive years. Consistency was found between individuals across time in timing of the seaward migration. Individuals migrating early during their first migration tended to migrate early the following years, and late migrants tended to migrate late. The same pattern was found also at ascent to freshwater. Hence, this study demonstrated that individual fish in nature can differ in behavior related to migration timing and that these differences can be consistent during their lifetime. Early migrants increased their mass more than late migrants and had a higher specific growth rate. Early migrating Arctic char, but not brown trout, experienced a longer life after the first migration to sea than late migrants. In both species, maturity occurred earlier in individuals that migrated early. For brown trout, but not for Arctic char, fecundity was significantly correlated to the timing of smolt migration. Hence, the repeatable individual variation in migration timing seemed to have ecological and fitness consequences in terms of growth, longevity, timing of maturity, and lifetime fecundity. [ABSTRACT FROM AUTHOR]

Adaptive radiation is the diversification of species to different ecological niches and has repeatedly occurred in different salmonid fish of postglacial lakes. In Lake Tinnsjøen, one of the largest and deepest lakes in Norway, the salmonid fish, Arctic charr (Salvelinus alpinus (L.)), has likely radiated within 9,700 years after deglaciation into ecologically and genetically segregated Piscivore, Planktivore, Dwarf, and Abyssal morphs in the pelagial, littoral, shallow‐moderate profundal, and deep‐profundal habitats. We compared trait variation in the size of the head, the eye and olfactory organs, as well as the volumes of five brain regions of these four Arctic charr morphs. We hypothesised that specific habitat characteristics have promoted divergent body, head, and brain sizes related to utilized depth differing in environmental constraints (e.g., light, oxygen, pressure, temperature, and food quality). The most important ecomorphological variables differentiating morphs were eye area, habitat, and number of lamellae. The Abyssal morph living in the deepest areas of the lake had the smallest brain region volumes, head, and eye size. Comparing the olfactory bulb with the optic tectum in size, it was larger in the Abyssal morph than in the Piscivore morph. The Piscivore and Planktivore morphs that use more illuminated habitats have the largest optic tectum volume, followed by the Dwarf. The observed differences in body size and sensory capacities in terms of vision and olfaction in shallow and deepwater morphs likely relates to foraging and mating habitats in Lake Tinnsjøen. Further seasonal and experimental studies of brain volume in polymorphic species are needed to test the role of plasticity and adaptive evolution behind the observed differences. [ABSTRACT FROM AUTHOR]

Possible effects of short‐term starvation on flesh quality in Arctic charr were studied in spring (March) and summer (August). Groups of juvenile Arctic charr (mean weight March 536 g ± 24; August 461 g ± 15 SEM) were starved for 1, 2 and 4 weeks (March) and 1, 2 and 3 (August). After each starvation period, the fish were slaughtered, and flesh samples collected in order to investigate quality and textural properties in the different experimental groups. Starvation had a positive effect on flesh quality giving firmer texture and lower gaping scores. Starved fish had lower cathepsin activity at slaughter, and a similar difference was seen one‐week post mortem. The results showed that the effect of starvation period was seasonally dependent. Starvation had a larger effect in summer, where a three‐week starvation resulted in firmer texture, whereas this was not seen during spring. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The article discusses Stable coexistence of native and non-native species can occur when non-native species colonize a "vacant niche" or when rapid niche shifts limit the overlap in resource use by native and non-native species. Topics include niche convergence can occur when native and non-native species coexist; and stable isotope niche overlap was the strongest for young-of-the-year individuals.

In 2018 and 2019, salmonid fishes, Salmo trutta L. and Salvelinus alpinus (L.) from lakes in Iceland were assessed for trematodes during a parasitological examination. Combined morphological and molecular analyses revealed the presence of four trematode species, two of which were previously known to parasitise salmonids in Iceland, Crepidostomum farionis (Müller, 1780) and Phyllodistomum umblae (Fabricius, 1780), and the two remaining species were recognised as new to science. Morphologically and genetically, Crepidostomum brinkmanni n. sp. and C. pseudofarionis n. sp. are closely related to two European species, namely C. metoecus and C. farionis. However, C. brinkmanni n. sp. is distinct by the position of maximum body width and arrangement of vitelline follicles; C. pseudofarionis n. sp. is distinct by its stout body, position of maximum body width, size of muscular papillae relative to oral sucker and the anterior extent of vitelline follicles. The new species were previously molecularly detected in their intermediate and definitive hosts in Norway and Ukraine, but their sequences were not supplemented with any morphological characterisation. In the present study, we provide detailed morphological descriptions and molecular sequences (28S rDNA and ITS2) of the four species of trematodes detected in Iceland. The discovery of the two new species of Crepidostomum indicates that the trematode diversity in fishes in the north is higher than previously known; our finding doubles the species spectrum of fish trematodes for Iceland. The record of C. brinkmanni from Ukraine indicates that its distribution might not be limited to northern latitudes. [ABSTRACT FROM AUTHOR]

The origin of species is a central topic in biology. Ecological speciation might be a driver in adaptive radiation, providing a framework for understanding mechanisms, level, and rate of diversification. The Arctic charr Salvelinus alpinus L. is a polymorphic species with huge morphological and life‐history diversity in Holarctic water systems. We studied adaptive radiation of Arctic charr in the 460‐m‐deep Lake Tinnsjøen to (a) document eco‐morphology and life‐history traits of morphs, (b) estimate reproductive isolation of morphs, and (c) illuminate Holarctic phylogeography and lineages colonizing Lake Tinnsjøen. We compared Lake Tinnsjøen with four Norwegian outgroup populations. Four field‐assigned morphs were identified in Lake Tinnsjøen: the planktivore morph in all habitats except deep profundal, the dwarf morph in shallow‐moderate profundal, the piscivore morph mainly in shallow‐moderate profundal, and a new undescribed abyssal morph in the deep profundal. Morphs displayed extensive life‐history variation in age and size. A moderate‐to‐high concordance was observed among morphs and four genetic clusters from microsatellites. mtDNA suggested two minor endemic clades in Lake Tinnsjøen originating from one widespread colonizing clade in the Holarctic. All morphs were genetically differentiated at microsatellites (FST: 0.12–0.20), associated with different mtDNA clade frequencies. Analyses of outgroup lakes implied colonization from a river below Lake Tinnsjøen. Our findings suggest postglacial adaptive radiation of one colonizing mtDNA lineage with niche specialization along a depth–temperature–productivity–pressure gradient. Concordance between reproductive isolation and habitats of morphs implies ecological speciation as a mechanism. Particularly novel is the extensive morph diversification with depth into the often unexplored deepwater profundal habitat, suggesting we may have systematically underestimated biodiversity in lakes. In a biological conservation framework, it is imperative to protect endemic below‐species‐level biodiversity, particularly so since within‐species variation comprises an extremely important component of the generally low total biodiversity observed in the northern freshwater systems. [ABSTRACT FROM AUTHOR]

The Government of Canada has committed to protect 10% of its coastal and marine areas. One means of protection is through the development of Marine Protected Areas (MPAs). In Nunavut, Regional Inuit Associations along with other stakeholders provided guidance to identify potential Areas of Interest (AOI) for a Marine Protected Area process. In the Kivalliq Region of Nunavut, the marine waters adjacent to Southampton Island (SI) were identified as one AOI. The Southampton Island Ecologically and Biologically Significant Area (SI EBSA) provides valuable migratory habitat for Beluga (Delphinapterus leucas), Bowhead (Balaena mysticetus) and Narwhal (Monodon monoceros), as well as feeding and calving areas for a proportion of these marine mammal populations. The SI EBSA is home to large aggregations of seabirds such as the two colonies of Thick-Billed Murres (Uria lomvia) on Coats Island and the largest single colony of Common Eiders (Somateria mollissima) in Nunavut. Resident marine mammals to the SI EBSA include Walrus (Odobenus rosmarus) and Polar Bear (Ursus maritimus) populations. In addition, migratory Arctic Char (Salvelinus alpinus) are the most abundant salmonid that is available for subsistence harvesting to Inuit communities living adjacent to the SI EBSA. The recurring polynya in Roes Welcome Sound provides approximately 52 km2 of open water during winter and is believed to play an important role in deep water formation and nutrient cycling in Hudson Bay, which may support high benthic productivity, and in turn large numbers of migrating birds and marine mammals. The polynya also provides valuable overwintering habitat for Walruses, Bearded Seals (Erignathus barbatus), and small numbers of Belugas in some years. This document provides a summary and synthesis of existing information relevant to the SI EBSA which has been used to determine its ecological significance, as well as known knowledge gaps and vulnerabilities. [ABSTRACT FROM AUTHOR]

Arctic charr (Salvelinus alpinus) is a species of high economic value for the aquaculture industry, and of high ecological value due to its Holarctic distribution in both marine and freshwater environments. Novel genome sequencing approaches enable the study of population and quantitative genetic parameters even on species with limited or no prior genomic resources. Low coverage genotyping by sequencing (GBS) was applied in a selected strain of Arctic charr in Sweden originating from a landlocked freshwater population. For the needs of the current study, animals from year classes 2013 (171 animals, parental population) and 2017 (759 animals; 13 full sib families) were used as a template for identifying genome wide single nucleotide polymorphisms (SNPs). GBS libraries were constructed using the PstI and MspI restriction enzymes. Approximately 14.5K SNPs passed quality control and were used for estimating a genomic relationship matrix. Thereafter a wide range of analyses were conducted in order to gain insights regarding genetic diversity and investigate the efficiency of the genomic information for parentage assignment and breeding value estimation. Heterozygosity estimates for both year classes suggested a slight excess of heterozygotes. Furthermore, FST estimates among the families of year class 2017 ranged between 0.009 - 0.066. Principal components analysis (PCA) and discriminant analysis of principal components (DAPC) were applied aiming to identify the existence of genetic clusters among the studied population. Results obtained were in accordance with pedigree records allowing the identification of individual families. Additionally, DNA parentage verification was performed, with results in accordance with the pedigree records with the exception of a putative dam where full sib genotypes suggested a potential recording error. Breeding value estimation for juvenile growth through the usage of the estimated genomic relationship matrix clearly outperformed the pedigree equivalent in terms of prediction accuracy (0.51 opposed to 0.31). Overall, low coverage GBS has proven to be a cost-effective genotyping platform that is expected to boost the selection efficiency of the Arctic charr breeding program. [ABSTRACT FROM AUTHOR]

Understanding the genomic basis of adaptative intraspecific phenotypic variation is a central goal in conservation genetics and evolutionary biology. Lake trout (Salvelinus namaycush) are an excellent species for addressing the genetic basis for adaptive variation because they express a striking degree of ecophenotypic variation across their range; however, necessary genomic resources are lacking. Here we utilize recently-developed analytical methods and sequencing technologies to (1) construct a high-density linkage and centromere map for lake trout, (2) identify loci underlying variation in traits that differentiate lake trout ecophenotypes and populations, (3) determine the location of the lake trout sex determination locus, and (4) identify chromosomal homologies between lake trout and other salmonids of varying divergence. The resulting linkage map contains 15,740 single nucleotide polymorphisms (SNPs) mapped to 42 linkage groups, likely representing the 42 lake trout chromosomes. Female and male linkage group lengths ranged from 43.07 to 134.64 centimorgans, and 1.97 to 92.87 centimorgans, respectively. We improved the map by determining coordinates for 41 of 42 centromeres, resulting in a map with 8 metacentric chromosomes and 34 acrocentric or telocentric chromosomes. We use the map to localize the sex determination locus and multiple quantitative trait loci (QTL) associated with intraspecific phenotypic divergence including traits related to growth and body condition, patterns of skin pigmentation, and two composite geomorphometric variables quantifying body shape. Two QTL for the presence of vermiculations and spots mapped with high certainty to an arm of linkage group Sna3, growth related traits mapped to two QTL on linkage groups Sna1 and Sna12, and putative body shape QTL were detected on six separate linkage groups. The sex determination locus was mapped to Sna4 with high confidence. Synteny analysis revealed that lake trout and congener Arctic char (Salvelinus alpinus) are likely differentiated by three or four chromosomal fissions, possibly one chromosomal fusion, and 6 or more large inversions. Combining centromere mapping information with putative inversion coordinates revealed that the majority of detected inversions differentiating lake trout from other salmonids are pericentric and located on acrocentric and telocentric linkage groups. Our results suggest that speciation and adaptive divergence within the genus Salvelinus may have been associated with multiple pericentric inversions occurring primarily on acrocentric and telocentric chromosomes. The linkage map presented here will be a critical resource for advancing conservation oriented genomic research on lake trout and exploring chromosomal evolution within and between salmonid species. [ABSTRACT FROM AUTHOR]

Changes in abiotic and biotic factors between seasons in subarctic lake systems are often profound, potentially affecting the community structure and population dynamics of parasites over the annual cycle. However, few winter studies exist and interactions between fish hosts and their parasites are typically confined to snapshot studies restricted to the summer season whereas host‐parasite dynamics during the ice‐covered period rarely have been explored. The present study addresses seasonal patterns in the infections of intestinal parasites and their association with the diet of sympatric living Arctic charr (Salvelinus alpinus) and brown trout (Salmo trutta) in Lake Takvatn, a subarctic lake in northern Norway. In total, 354 Arctic charr and 203 brown trout were sampled from the littoral habitat between June 2017 and May 2018. Six trophically transmitted intestinal parasite taxa were identified and quantified, and their seasonal variations were contrasted with dietary information from both stomachs and intestines of the fish. The winter period proved to be an important transmission window for parasites, with increased prevalence and intensity of amphipod‐transmitted parasites in Arctic charr and parasites transmitted through fish prey in brown trout. In Arctic charr, seasonal patterns in parasite infections resulted mainly from temporal changes in diet toward amphipods, whereas host body size and the utilization of fish prey were the main drivers in brown trout. The overall dynamics in the community structure of parasites chiefly mirrored the seasonal dietary shifts of their fish hosts. [ABSTRACT FROM AUTHOR]

The resiliency of populations and species to environmental change is dependent on the maintenance of genetic diversity, and as such, quantifying diversity is central to combating ongoing widespread reductions in biodiversity. With the advent of next‐generation sequencing, several methods now exist for resolving fine‐scale population structure, but the comparative performance of these methods for genetic assignment has rarely been tested. Here, we evaluate the performance of sequenced microsatellites and a single nucleotide polymorphism (SNP) array to resolve fine‐scale population structure in a critically important salmonid in north eastern Canada, Arctic Charr (Salvelinus alpinus). We also assess the utility of sequenced microsatellites for fisheries applications by quantifying the spatial scales of movement and exploitation through genetic assignment of fishery samples to rivers of origin and comparing these results with a 29‐year tagging dataset. Self‐assignment and simulation‐based analyses of 111 genome‐wide microsatellite loci and 500 informative SNPs from 28 populations of Arctic Charr in north‐eastern Canada identified largely river‐specific genetic structure. Despite large differences (~4X) in the number of loci surveyed between panels, mean self‐assignment accuracy was similar with the microsatellite loci and the SNP panel (>90%). Subsequent analysis of 996 fishery‐collected samples using the microsatellite panel revealed that larger rivers contribute greater numbers of individuals to the fishery and that coastal fisheries largely exploit individuals originating from nearby rivers, corroborating results from traditional tagging experiments. Our results demonstrate the efficacy of sequence‐based microsatellite genotyping to advance understanding of fine‐scale population structure and harvest composition in northern and understudied species. [ABSTRACT FROM AUTHOR]

Acoustic and archival telemetry were used to study the marine movements of 115 anadromous Arctic char (Salvelinus alpinus) at two sites in southern Labrador, Canada, in relation to daily variation in temperature and depth use, body size, and their effects on marine activity patterns. Although evidence varied between locations, Arctic char generally utilized ambient water temperatures available in the upper water column, possibly in aid of physiological processes such as digestion, whereas deeper waters were suggested to be used for feeding purposes. Size-dependent thermal preferences were evident, with larger individuals utilizing cooler water temperatures (8.5 °C) compared with smaller individuals (9.5 °C), a pattern suggestive of ontogenetic changes in thermal habitat use for the purposes of growth maximization. Diurnal patterns of diving activity were interpreted to reflect the vertical migration of prey items and (or) the visual capabilities of Arctic char. Dive duration was dependent on body size and external body temperature with smaller individuals performing shorter dives in colder water temperatures (<1 min at 5 °C) than larger fish (∼2 min at 5 °C), likely to maintain their core temperature and abilities to both effectively capture prey and avoid predation. [ABSTRACT FROM AUTHOR]

Understanding the extent to which ecological divergence is repeatable is essential for predicting responses of biodiversity to environmental change. Here we test the predictability of evolution, from genotype to phenotype, by studying parallel evolution in a salmonid fish, Arctic charr (Salvelinus alpinus), across eleven replicate sympatric ecotype pairs (benthivorous-planktivorous and planktivorous-piscivorous) and two evolutionary lineages. We found considerable variability in eco-morphological divergence, with several traits related to foraging (eye diameter, pectoral fin length) being highly parallel even across lineages. This suggests repeated and predictable adaptation to environment. Consistent with ancestral genetic variation, hundreds of loci were associated with ecotype divergence within lineages of which eight were shared across lineages. This shared genetic variation was maintained despite variation in evolutionary histories, ranging from postglacial divergence in sympatry (ca. 10-15kya) to pre-glacial divergence (ca. 20-40kya) with postglacial secondary contact. Transcriptome-wide gene expression (44,102 genes) was highly parallel across replicates, involved biological processes characteristic of ecotype morphology and physiology, and revealed parallelism at the level of regulatory networks. This expression divergence was not only plastic but in part genetically controlled by parallel cis-eQTL. Lastly, we found that the magnitude of phenotypic divergence was largely correlated with the genetic differentiation and gene expression divergence. In contrast, the direction of phenotypic change was mostly determined by the interplay of adaptive genetic variation, gene expression, and ecosystem size. Ecosystem size further explained variation in putatively adaptive, ecotype-associated genomic patterns within and across lineages, highlighting the role of environmental variation and stochasticity in parallel evolution. Together, our findings demonstrate the parallel evolution of eco-morphology and gene expression within and across evolutionary lineages, which is controlled by the interplay of environmental stochasticity and evolutionary contingencies, largely overcoming variable evolutionary histories and genomic backgrounds. Author summary: A renowned natural model system for adaptive evolution is the repeated and rapid divergence of fishes into different sympatric trophic and morphological specialists, known as ecotypes. The drivers and constraints of these repeated divergences are complex and not well understood but it is often observed that postglacial fishes diverge in predictable patterns. Here we use a framework of parallel (or convergent) evolution to test the predictability of divergence in the most variable northern freshwater fish, the Arctic charr. Using a hierarchy of replication—from individuals to divergent phylogeographic lineages—we detect parallel evolution of foraging-related traits despite variation in genomic backgrounds and evolutionary histories. The level of phenotypic parallelism can be explained by the complex interplay of environment, shared genetic variation, and variability in gene expression. While phenotypic divergence may be determined and/or constraint by genetic and molecular divergence, the direction of change is largely determined by molecular parallelism and shared adaptive genetic variation. These are in turn associated with environmental similarity, reflected as ecosystem size. We suggest that gene expression facilitates parallel ecotype evolution, but that the extent of parallelism is further influenced by the level of shared genetic variation and ecological opportunity. [ABSTRACT FROM AUTHOR]

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 δ13C values) of essential amino acids (EAAs) isolated from DBS, liquid whole blood, and muscle. The δ13C values of 5 EAAs (δ13CEAAs; isoleucine [Ile], leucine [Leu], phenylalanine [Phe], valine [Val], and threonine [Thr]) from DBS were highly correlated with δ13CEAAs of liquid whole blood (r2 range = 0.693–0.895) and muscle (r2 range = 0.642–0.881). The patterns of δ13CEAAs 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 [ABSTRACT FROM AUTHOR]

The short‐ and long‐term effects of altered photoperiods during winter on growth and final gonadosomatic index (GSI) were investigated in 178 individually tagged 2‐year‐old smolt Arctic charr from an anadromous strain. The fish were reared at ambient temperature (2.3–12.5°C) for 18 months and reared at five different photoperiods. One group was reared on constant LD16:8 (light–dark, N = 40) photoperiod and a second group on continuous light (LD24:0, N = 32) throughout the experimental period. Three groups of fish were moved from LD16:8 to LD24:0 for 44 days and subsequently back to LD16:8, that is early winter light group (Early WL: 17 November–5 January; N = 35), Mid WL group (5 January–23 February; N = 38) and Late WL group (23 February–6 April; N = 33). No differences in growth were found for females, whereas males reared at constant LD24:0 were larger (mean ± SEM, 1,780 g ± 180) compared with the Late (1,264 g ± 101) and Mid WL (1,413 g ± 120) groups towards the end the study. Exposure to continuous light during early winter significantly influenced the GSI in female Arctic charr, whereas no differences were found in the males. Female GSI (%) was lowest in the Mid WL group (1.7) and highest in the LD24:0 group (7.0). In conclusion, the present study demonstrated that application of brief continuous light treatments during January and February can possibly be used as a tool to lower subsequent female maturation in Arctic charr farming. [ABSTRACT FROM AUTHOR]

Life history strategies and potential marine niche use of Arctic charr Salvelinus alpinus (n = 237, 84–652 mm, total body length, LT) were determined during the ice‐free season (2012) at three different watercourses in south‐western Greenland. All Arctic charr were collected from freshwater habitats. Based on stable isotopes of δ34S, the Arctic charr were categorized as either marine‐ or freshwater‐dependent feeders. The use of time‐integrated trophic tracers (stable isotopes of δ13C, δ15N, δ34S) suggested that several trophic groups of Arctic charr operate alongside within each fjord system. The groups suggested were one group that specialized in the marine habitat, in addition to two freshwater resident morphs (small‐sized resident and/or large‐growing cannibalistic individuals). Stomach contents consisted entirely of freshwater and terrestrial prey (i.e., insects), indicating that marine‐dependent feeders also fed in freshwater habitats after return from their marine migration. Growth and maturity patterns further supported variable life history strategies within each watercourse. The life history strategy patterns and marine trophic niche use were consistent across the watercourses along several hundred kilometres of coastline. This study represents the first ecological baseline for partially anadromous populations of Greenland Arctic charr. [ABSTRACT FROM AUTHOR]

Ecosystems at high latitudes are exposed to some of the highest rates of climate warming on earth, and freshwater ecosystems in those regions are already experiencing extended ice‐free seasons and warmer waters. The dominant fish species in these ecosystems are cold‐water salmonids, which play a central ecological role in lake ecosystems, where they are often exposed to size‐selective fisheries that truncate their size and age distributions, making them potentially vulnerable to exploitation and environmental perturbations.Here, we address the combined effects of climate‐induced water temperature increase (using regionally downscaled climate models based on the RCP‐4.5 and RCP‐8.5 climate scenarios together with an air‐to‐water temperature model) and gillnet harvesting, over the period from 1950 to 2100, on the somatic growth, demography and vulnerability of Arctic charr Salvelinus alpinus (L.), using an eco‐genetic individual‐based model. The model captures successive annual life‐history events, including the key processes of size‐dependent mortality, age‐ and size‐dependent maturation described by a probabilistic reaction norm, temperature‐dependent growth, size‐dependent reproduction and density‐dependent recruitment.Our model predicts that higher water temperatures will increase the somatic growth of Arctic charr, leading to larger body size at age and increased stock biomass: for RCP‐8.5, we predict an 80% increase in stock biomass in the year 2100 relative to the year 2000 in the absence of fishing. Interestingly, this potential increase in biomass in future climate scenarios will be partially masked by harvesting: for a fishing mortality of 0.3 year−1, we predict a mere 40% increase in stock biomass in 2100 relative to 2000. Despite the predicted increase in stock biomass, yield will increase substantially only when fishing mortality is low. In addition, climate warming will accentuate the age‐truncation effect of harvesting, which will target younger individuals, including immatures, thus elevating the vulnerability of the population to environmental perturbations.Synthesis and applications. Our model‐based analyses highlight the combined effects of climate change and size‐selective fishing, emphasizing the emerging vulnerability of fish populations to multiple stressors. We recommend carefully climate‐adapted management strategies permitting only a narrow range of gillnet mesh sizes for inland fisheries at high latitudes. [ABSTRACT FROM AUTHOR]

The effect of elevation gradient on characteristics of aquatic communities has been studied in the basin of the Vangyr River, a third-order tributary of the Pechora River. The results show that the orders of amphibiotic insects characteristic of the rhithron zone prevail in the zoobenthos. The composition of hydrobiont fauna slightly changes with increasing distance from the upper reaches of the river to its mouth, but the main insect families remain the same. The structure of fish community largely depends on the position of river segments and lakes in the elevation gradient. Only one species—Arctic char, a probable glacial relict—has been found at the sources of the Vangyr. Fish communities in many mountain lakes are monospecific. The ichthyofauna becomes gradually enriched as the river mouth is approached: there appears another glacial relict (peled) and anadromous and semianadromous species (Atlantic salmon and Siberian whitefish). [ABSTRACT FROM AUTHOR]

The Arctic will be especially affected by climate change, resulting in altered seasonal timing. Anadromous Arctic char (Salvelinus alpinus) is strongly influenced by sea surface temperature (SST) delimiting time periods available for foraging in the sea. Recent studies of salmonid species have shown variation at phenology‐related loci associated with timing of migration and spawning. We contrasted genetic population structure at 53 SNPs versus four phenology‐related loci among 15 anadromous Arctic char populations from Western Greenland and three outgroup populations. Among anadromous populations, the time period available for foraging at sea (>2°C) ranges from a few weeks to several months, motivating two research questions: (a) Is population structure compatible with possibilities for evolutionary rescue of anadromous populations during climate change? (b) Does selection associated with latitude or SST regimes act on phenology‐related loci? In Western Greenland, strong isolation by distance at SNPs was observed and spatial autocorrelation analysis showed genetic patch size up to 450 km, documenting contingency and gene flow among populations. Outlier tests provided no evidence for selection at phenology‐related loci. However, in Western Greenland, mean allele length at OtsClock1b was positively associated with the time of year when SST first exceeded 2°C and negatively associated with duration of the period where SST exceeded 2°C. This is consistent with local adaptation for making full use of the time period available for foraging in the sea. Current adaptation may become maladaptive under climate change, but long‐distance connectivity of anadromous populations could redistribute adaptive variation across populations and lead to evolutionary rescue. [ABSTRACT FROM AUTHOR]