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Background: The ice-free season (typically late-June to early-October) is crucial for anadromous species of fish in the Arctic, including Arctic Char (Salvelinus alpinus), which must acquire adequate resources for growth, reproduction, and survival during a brief period of feeding in the marine environment. Arctic Char is an important food fish for Inuit communities across the Arctic. Understanding drivers and patterns of migration in the marine environment is thus essential for conservation and management of the species. Methods: We used passive acoustic telemetry to characterize migration patterns of 51 individual anadromous Arctic Char during the ice-free season in the marine environment of Coronation Gulf (Nunavut, Canada; 2019–2022). Based on recent genetic evidence, some tagged individuals were likely Dolly Varden (Salvelinus malma malma), a closely related species to Arctic Char. Using local Getis G* and network analysis, we described movement patterns and identified high-use locations in the marine environment. We also related freshwater overwintering location to migration timing and movement pattern. Results: Comparing groups of fish that overwintered in distinct locations, we found: (i) limited evidence that marine movements were associated with overwintering location; (ii) minor differences in use of marine space; and, (iii) timing of freshwater return differed significantly between overwintering groups, and was related to length and difficulty of the migratory pathway in freshwater. Results from both network analysis and local Getis G* revealed that, regardless of overwintering location, coastal locations were highly used by fish. Conclusions: Overwintering locations, and the migratory routes to access overwintering locations, affect the timing of freshwater return. Preference of fish for coastal marine locations is likely due to abundance of forage and patterns in break-up of sea ice. Similarities in marine space use and movement patterns present challenges for managing this and other mixed stock fisheries of anadromous Salvelinus spp. Absences or periods of time when fish were not detected prevented comprehensive assessment of movement patterns. Local Getis G*, a local indicator of spatial association, is a helpful tool in identifying locations associated with absences in acoustic telemetry arrays, and is a complementary method to network analysis. [ABSTRACT FROM AUTHOR]

Climate‐driven changes including rising air temperatures, enhanced permafrost degradation, and altered precipitation patterns can have profound effects on contaminants, such as mercury (Hg), in High Arctic lakes. Two physically similar lakes, East Lake and West Lake at the Cape Bounty Arctic Watershed Observatory on Melville Island, Nunavut, Canada are being affected by climate change differently. Both lakes have experienced permafrost degradation in their catchments; however, West Lake has also undergone multiple underwater Mass Movement Events (MMEs; beginning in fall 2008), leading to a sustained 50‐fold increase in turbidity. This provided the unique opportunity to understand the potential impacts of permafrost degradation and other climate‐related effects on Hg concentrations and body condition of landlocked Arctic char (Salvelinus alpinus), an important sentinel species across the Circum‐Arctic. Our objectives were to assess temporal trends in char Hg concentrations and to determine potential mechanisms driving the trends. There was a significant decrease in Hg concentrations in East Lake char, averaging 6.5%/year and 3.8%/year for length‐adjusted and age‐adjusted means, respectively, from 2008 to 2019. Conversely, in West Lake there was a significant increase, averaging 7.9%/year and 8.0%/year for length‐adjusted and age‐adjusted mean Hg concentrations, respectively, for 2009 to 2017 (the last year with sufficient sample size). The best predictors of length‐adjusted Hg concentrations in West Lake were carbon and nitrogen stable isotope ratios, indicating a shift in diet including possible dietary starvation brought on by the profound increase in lake turbidity. Our study provides an example of how increasing lake turbidity, a likely consequence of climate warming in Arctic lakes, may influence fish condition and Hg concentrations. Environ Toxicol Chem 2023;42:2712–2725. © 2023 His Majesty the King in Right of Canada and The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada. [ABSTRACT FROM AUTHOR]

In the region of King William Island, Nunavut, in the Canadian high Arctic, populations of salmonids including Arctic char (Salvelinus alpinus), cisco (Coregonus autumnalis and C. sardinella) as well as lake whitefish (C. clupeaformis) are diadromous, overwintering in freshwater and transitioning to saline waters following ice melt. Since these fish were sampled at the same time and from the same traditional fishing sites, comparison of their skin structures, as revealed by 16S rRNA gene sequencing, has allowed an assessment of influences on wild fish bacterial communities. Arctic char skin microbiota underwent turnover in different seasonal habitats, but these striking differences in dispersion and diversity metrics, as well as prominent taxa involving primarily Proteobacteria and Firmicutes, were less apparent in the sympatric salmonids. Not only do these results refute the hypothesis that skin communities, for the most part, reflect water microbiota, but they also indicate that differential recruitment of bacteria is influenced by the host genome and physiology. In comparison to the well-adapted Arctic char, lake whitefish at the northern edge of their range may be particularly vulnerable, and we suggest the use of skin microbiomes as a supplemental tool to monitor a sustainable Indigenous salmonid harvest during this period of change in the high Arctic. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Bycatch in fisheries remains one of the biggest conservation threats to seabirds globally, but there has been limited attention given to bycatch in the Arctic. Here, we worked with Inuit commercial fishers in the Cambridge Bay region of Nunavut to record bycatch of birds as part of a fish bycatch reporting initiative, in weir and gill‐net fisheries that target anadromous Arctic Char Salvelinus alpinus. Weir fisheries, and one of the gill‐net fisheries (executed in freshwater), had no bird bycatch, but 291 loons (family Gavidae) were captured over 5 years in one estuarine–marine fishery, yielding an exceptionally high bycatch rate of 15.7 birds/1,000 net‐meter‐days. One of the species caught, the yellow‐billed loon Gavia adamsii, is considered near threatened, but data on the population status of this species is insufficient to determine whether bycatch forms a significant threat. Nonetheless, deterrence efforts or other conservation options are needed in estuarine gill‐net fisheries to reduce bird bycatch. [ABSTRACT FROM AUTHOR]

Arctic char (Salvelinus alpinus) is a facultatively anadromous fish species that is critically important to many Inuit communities in the Canadian Arctic. Plasticity in life history has allowed the species to persist in a diversity of challenging Holarctic environments. Despite their ecological and cultural importance and their presence in aquatic ecosystems that are ice‐covered for much of the year, few under‐ice studies of Arctic char have been conducted. Most winter studies of adult Arctic char have focused on lakes, where they typically overwinter. Several populations of Arctic char, however, overwinter in large river systems, and subsistence fishers have reported that Arctic char overwinter in the lower reaches of the Coppermine River. The Coppermine River is a large Arctic river that flows into Coronation Gulf near Kugluktuk, Nunavut, Canada. The authors used acoustic telemetry to investigate the overwintering ecology of Arctic char in the region. Consistent with local knowledge, they detected Arctic char overwintering within the fluvial environment of the Coppermine River from 2018 to 2020. Unlike other fluvial environments known to be used by overwintering Arctic char, the lower reaches of the Coppermine River are completely ice‐covered throughout the winter, are of moderate depths (3.8–14.1 m) and have no known groundwater inputs. Acoustic telemetry observations indicated long‐distance movement (7–8 km) within the river in early winter (October) in response to dynamic ice formation. Under‐ice movement generally declined 2 weeks after river freeze‐up but continued throughout winter in the lower 5 km of the river, where there were fewer under‐ice disturbances. Migration into the marine environment before river ice break‐up (June), as well as winter (November–May) movements into and within the marine environment, was unexpectedly observed for some fish. Under‐ice use of the marine environment is unusual for Arctic char at the distances observed (up to 18 km) and has not previously been documented at the temperatures (fish body temperatures from −0.76 to 1.90°C) observed. Results allow further understanding of the diverse life‐history tactics employed by Arctic char and lay a foundation for future research into fluvial and other diverse overwintering tactics employed by the species. [ABSTRACT FROM AUTHOR]

Two related salmonids, Arctic char (Salvelinus alpinus) and lake whitefish (Coregonus clupeaformis) sampled from the high Arctic region of Nunavut, Canada are anadromous fish, migrating annually from the same ice‐covered freshwater waterbodies to spend summers in the marine waters of the Arctic Ocean. Microbiota associated with the skin‐associated mucus undergo community change coincident with migration, and irrespective of this turnover, antibiotic resistance was detected in mixed bacterial cultures initiated with mucus samples. Although as expected most bacteria were unculturable, however, 5/7 isolates showed susceptibility to a panel of five common antibiotics. The fish were sampled under severe conditions and at remote locations far from human habitation. Regardless, two isolates, 'Carnobacterium maltaromaticum sm‐2' and 'Arthrobacter citreus sm', showed multi‐resistance to two or more antibiotics including ampicillin and streptomycin indicating multiple resistance genes. It is unknown if these fish bacteria have 'natural' resistance phenotypes or if resistance has been acquired. As result of these observations, we urge long‐term monitoring of drug‐resistant bacteria in the region and caution the assumption of a lack of drug‐resistant organisms even in such extreme environments. [ABSTRACT FROM AUTHOR]

The "genomics era" has allowed questions to be asked about genome organization and genome architecture of non-model species at a rate not previously seen. Analyses of these genome-wide datasets have documented many examples of novel structural variants (SVs) such as chromosomal inversions, copy number variants, and chromosomal translocations, many of which have been linked to adaptation. The salmonids are a taxonomic group with abundant genome-wide datasets due to their importance in aquaculture and fisheries. However, the number of documented SVs in salmonids is surprisingly low and is most likely due to removing loci in high linkage disequilibrium when analyzing structure and gene flow. Here we re-analyze RAD-seq data from several populations of Arctic charr (Salvelinus alpinus) and document a novel ~1.2 MB SV at the distal end of LG12. This variant contains 15 protein-coding genes connected to a wide-range of functions including cell adhesion and signal transduction. Interestingly, we studied the frequency of this polymorphism in four disjointed populations of charr--one each from Nunavut, Newfoundland, Eastern Russia, and Scotland--and found evidence of the variant only in Nunavut, Canada, suggesting the polymorphism is novel and recently evolved. [ABSTRACT FROM AUTHOR]

Killer whales (Orcinus orca) historically restricted to certain Arctic regions due to extensive sea ice have recently been documented farther north and for longer durations in the Canadian Arctic. These apex predators accumulate high levels of persistent organic pollutants (POPs). The objective of this study was to evaluate the concentrations and profiles of POPs in killer whales of the Canadian Arctic, thus determining potential risks for Inuit communities if consumed. Biopsies were collected from 33 killer whales across areas of the Canadian Arctic between 2009 and 2021. Significant variability in POP concentrations was observed among whales. The cumulative POP concentrations ranged from 12 to >2270 mg/kg lw, representing ∼200-fold increase from the least to the most contaminated individual. The rank order of concentrations of the top five contaminant classes was ∑DDT, ∑PCB, ∑CHL, ∑Toxaphene, and Dieldrin. Several emerging Arctic contaminants were detected, including chlorpyrifos, endosulfan, pentachloroanisole, and polychlorinated naphthalenes, although at relatively lower concentrations than legacy POPs. Considering the elevated blubber POP levels in killer whales, recommended daily consumption thresholds, established based on human tolerable daily intake (TDI) values, were notably restricted for ∑PCB (<0.14 g), ∑DDT (<6.9 g), ∑CHL (<13 g), dieldrin (<8 g) and heptachlor epoxide (<5 g). Killer whales in the Canadian Arctic exhibited higher POP concentrations than other commonly hunted species such as polar bears, ringed seals, and Arctic char. We acknowledge that a more holistic risk assessment of diet is required to assess the cumulative impacts of contaminant mixtures as well as nutritional quality of tissues commonly consumed by northern communities. [Display omitted] • Climate change is increasing Inuit interactions with killer whales in the Canadian Arctic. • Some Nunavut communities within the Qikiqtaaluk region have expressed interest in hunting killer whales. • 200-fold difference in sum POPs from least to most contaminated killer whale blubber. • Killer whale contaminant levels far higher than traditional country foods. • Safe human consumption of killer whale blubber is limited to <0.1–10 g per day. [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]

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 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]

Despite immense concern over amplified warming in the Arctic, physiological research to address related conservation issues for valuable cold-adapted fish, such as the Arctic char (Salvelinus alpinus), is lacking. This crucial knowledge gap is largely attributable to the practical and logistical challenges of conducting sensitive physiological investigations in remote field settings. Here, we used an innovative, mobile aquatic-research laboratory to assess the effects of temperature on aerobic metabolism and maximum heart rate (f Hmax) of upriver migrating Arctic char in the Kitikmeot region of Nunavut in the central Canadian Arctic. Absolute aerobic scope was unchanged at temperatures from 4 to 16°C, while f Hmax increased with temperature (Q 10 = 2.1), as expected. However, f Hmax fell precipitously below 4°C and it began to plateau above ~ 16°C, reaching a maximum at ~ 19°C before declining and becoming arrhythmic at ~ 21°C. Furthermore, recovery from exhaustive exercise appeared to be critically impaired above 16°C. The broad thermal range (~4–16°C) for increasing f Hmax and maintaining absolute aerobic scope matches river temperatures commonly encountered by migrating Arctic char in this region. Nevertheless, river temperatures can exceed 20°C during warm events and our results confirm that such temperatures would limit exercise performance and thus impair migration in this species. Thus, unless Arctic char can rapidly acclimatize or alter its migration timing or location, which are both open questions, these impairments would likely impact population persistence and reduce lifetime fitness. As such, future conservation efforts should work towards quantifying and accounting for the impacts of warming, variable river temperatures on migration and reproductive success. [ABSTRACT FROM AUTHOR]

Harvesting from admixed populations is a common practice in contemporary fisheries. However, monitoring stock health in such mixed-stock fisheries remains challenging, with accurately identifying stock composition a critical first step. Fortunately, genetic tools have improved our ability to quantify stock composition ("genetic stock identification" or GSI). A commercial Arctic char (Salvelinus alpinus) fishery has been proposed for the King William Island region of the Lower Northwest Passage (LNWP), Nunavut, Canada, an area that heretofore has had only subsistence fisheries. Previous studies identified two major char genetic clusters in this region with evidence of stock mixing in some rivers and estuaries. We developed a panel of 181 autosomal single nucleotide polymorphisms and one sex marker using Genotyping-in-Thousands by sequencing (GTseq) to facilitate GSI and sex identification and contribute to development of a sustainable fishery. Applying population genetics and population assignment tests to a pilot set of 48 samples, our panel proved effective in GSI with an assignment success rate of 95.8–100%, and in sex determination with a success rate of 93.6%. Our panel of 182 markers provides a cost- and time-efficient means to perform GSI and sex identification in char in the LNWP, which in turn can be used for effective, continuous monitoring of Arctic char in this region. Collectively, a sustainable Arctic char fishery could bring both long-term revenue and a stable food source to the Inuit community of Gjoa Haven. • Arctic char populations from King William Island and adjacent Chantrey Inlet, Nunavut are genetically differentiated. • A new char fishery requires tools for effective fisheries management of the two identified stocks. • We develop and test a multi-amplicon GTseq tool to facilitate stock identification and sex determination. • Our GTSeq panel allows for fast and accurate stock composition assessment for future fisheries management. [ABSTRACT FROM AUTHOR]

Abstract: A snapshot sample of Arctic charr (Salvelinus alpinus) from Heintzelman Lake (81°42′N, 66°56′W), Ellesmere Island, Canada was used to elucidate the biological and life-history factors potentially influencing individual total mercury (THg) concentrations. Migratory history was significant, with anadromous fish having a lower mean THg concentration (64μg/kg ww) than the non-anadromous Arctic charr (117μg/kg ww). The increase in individual THg concentration with age was shown to be independent of length-at-age when large and small individuals within the same age groups were compared. Similarly, the diets of individual Arctic charr were comparable regardless of size, and there was no apparent ontogenetic shift in diet that could explain differences in length-at-age or THg concentration among fast- and slow-growing groups of fish (i.e., fish of the same age but differing sizes). Maturity state was also not related to THg concentration, but appears to be related to differences in length-at-age, with slow-growing fish allocating more energy to reproduction than fast-growing conspecifics. The differences in THg concentration among individual Arctic charr were best explained by fish age. We suggest that the increase in mercury concentration with age can be altered by a shift in diet (e.g., to piscivory) or habitat (e.g., anadromy), but is otherwise unaffected by changes in size or length-at-age. [Copyright &y& Elsevier]

- Owing to limited knowledge of the habitat use and diet of juvenile Arctic charr from the High Arctic, particularly young-of-the-year (YOY), we assembled data obtained from samples taken in and around Lake Hazen, Nunavut, Canada, to assess juvenile habitat use and feeding. Juvenile charr demonstrated a preference for stream environments, particularly those fed by warm upstream ponds. Charr occupying both stream and nearshore lake habitats were found to feed similarly, with chironomids occurring most frequently in diets. Some older stream-dwelling charr preyed on smaller, younger Arctic charr. Preferred stream occupancy is likely mediated by physical barriers created mainly by water velocity, and by distance from the lake, lake-ice dynamics, low water depth, and turbidity. Water velocities resulted in stream habitat segregation by size, with YOY mainly found in low-velocity pools and back eddies adjacent to stream banks, but not in water velocities >0.1 m·s−1. Greatest charr densities in streams were found in small, shallow, slow-flowing side channels, which are highly susceptible to drought. Under predicted climate change scenarios, streams fed by small ponds will be susceptible to intermittent flow conditions, which could result in increased competition among juvenile charr for the remaining stream habitats. In addition, glacier-fed streams are likely to experience increased flow conditions that will exacerbate physical barriers created by water velocity and further reduce the availability of preferred stream habitat. [ABSTRACT FROM AUTHOR]

The Arctic charr Salvelinus alpinus is a diverse and abundant resource in Canada's Nunavut. The anadromous form is primarily targeted by exploitation in small-scale fisheries. The continued importance of subsistence fisheries and growing interest in further developing commercial fisheries underline the need for proper management of S. alpinus in northern Canada. This paper presents the current state of S. alpinus fisheries in Nunavut and related management challenges. An alternate framework for assessment using life-history information as it determines stock productivity and resilience to harvesting is presented. This framework combines (1) a risk assessment tool [productivity-susceptibility analysis (PSA)] to evaluate the relative vulnerability of S. alpinus stocks to harvest and (2) a conceptual model for quantitative assessment to determine sustainable harvest levels. Diversity in S. alpinus life history and contrast in vulnerability scores derived from PSA assessment are demonstrated for a sample of 86 anadromous stocks from throughout Nunavut. These data provide evidence in support of an alternate strategy for assessment permitting to integrate diversity in S. alpinus life history for improved generalization and representativeness. Salvelinus alpinus fisheries in Arctic regions exemplify the need for stock assessment and management alternatives to ensure fish conservation in remote, sensitive ecosystems and in data-poor circumstances. [ABSTRACT FROM AUTHOR]

Mercury concentrations ([Hg]) in Arctic food fish often exceed guidelines for human subsistence consumption. Previous research on two food fish species, Arctic char ( Salvelinus alpinus) and lake trout ( Salvelinus namaycush), indicates that anadromous fish have lower [Hg] than nonanadromous fish, but there have been no intraregional comparisons. Also, no comparisons of [Hg] among anadromous (sea-run), resident (marine access but do not migrate), and landlocked (no marine access) life history types of Arctic char and lake trout have been published. Using intraregional data from 10 lakes in the West Kitikmeot area of Nunavut, Canada, we found that [Hg] varied significantly among species and life history types. Differences among species-life history types were best explained by age-at-size and C:N ratios (indicator of lipid); [Hg] was significantly and negatively related to both. At a standardized fork length of 500 mm, lake trout had significantly higher [Hg] (mean 0.17 µg/g wet wt) than Arctic char (0.09 µg/g). Anadromous and resident Arctic char had significantly lower [Hg] (each 0.04 µg/g) than landlocked Arctic char (0.19 µg/g). Anadromous lake trout had significantly lower [Hg] (0.12 µg/g) than resident lake trout (0.18 µg/g), but no significant difference in [Hg] was seen between landlocked lake trout (0.21 µg/g) and other life history types. Our results are relevant to human health assessments and consumption guidance and will inform models of Hg accumulation in Arctic fish. Environ. Toxicol. Chem. 2011; 30:1459-1467. © 2011 SETAC [ABSTRACT FROM AUTHOR]

Multivariate morphometric analyses were used to examine variation in head, body, and fin shape between two sympatric morphotypes of Arctic char (Salvelinus alpinus (L., 1758)) from Lake Hazen, Ellesmere Island, Nunavut, Canada. Population structure of the Lake Hazen Arctic char was examined using five microsatellite loci. The 'small' morph was found to have a larger (primarily deeper) head, larger and more elongate fins, and a deeper lateral profile than the 'large' morph. The morphs also differed in allometric growth patterns. The large and small morphs do not appear to represent genetically distinct populations. The head morphology of the Lake Hazen small and large morphs exhibited similarities to benthic and pelagic morphs (respectively) from other lakes. We hypothesize that the large morph may be adapted to high-efficiency swimming and that the small morph may be adapted to low-efficiency, high-acceleration swimming. Such functional trade-offs are not uncommon among fish specializing in dispersed or mobile prey (fish and plankton) and benthic prey, respectively. The lack of apparent genetic differentiation between the morphs may suggest that the morphological differences result, to some extent, from phenotypic plasticity. Based on these results and previous analyses, it seems reasonable to conclude that Lake Hazen Arctic char represent a resource polymorphism. Des analyses morphométriques multidimensionnelles nous ont servi à étudier la variation de la forme de la tête, du corps et des nageoires chez deux morphotypes sympatriques de l'omble chevalier (Salvelinus alpinus (L., 1758)) du lac Hazen, île d'Ellesmere, Nunavut, Canada. Nous avons déterminé la structure de population des ombles chevaliers du lac Hazen par l'examen de cinq locus microsatellites. Le morphotype « petit » possède une tête plus grosse (surtout plus haute), des nageoires plus grandes et plus allongées et un profil latéral plus élevé que le morphotype « grand ». Les morphotypes diffèrent aussi par leurs patrons de croissance allométrique. Les morphotypes petit et grand ne semblent pas représenter des populations génétiquement distinctes. La morphologie de la tête des morphotypes petit et grand du lac Hazen rappelle les morphotypes (respectivement) benthique et pélagique décrits dans d'autres lacs. Nous émettons l'hypothèse selon laquelle le grand morphotype peut être adapté à la nage de grande efficacité et le petit morphotype l'est à la nage de faible efficacité, mais d'accélération rapide. De tels compromis fonctionnels ne sont pas rares chez les poissons qui se spécialisent respectivement pour les proies dispersées ou mobiles (poissons et plancton) et pour les proies benthiques. L'absence apparente de différenciation génétique entre les morphotypes peut laisser croire que les différences morphologiques proviennent, dans une certaine mesure, de la plasticité phénotypique. D'après nos résultats et des analyses antérieures, il semble raisonnable de conclure que les ombles chevaliers du lac Hazen présentent un polymorphisme basé sur les ressources. [ABSTRACT FROM AUTHOR]

Two life-history variants of Arctic charr ( Salvelinus alpinus), anadromous and lake-resident, have been previously identified in lakes of Southern Baffin Island, Nunavut, Canada. In accordance with classical life-history theory, it is hypothesised that anadromous charr will delay maturation in both size and age, and have increased fecundity (per spawning event) in comparison with lake-resident charr. Sagittal otoliths and biological data were collected for both life-history variants within the three studied lakes: Iqalugaarjuit, Qasigiat and Qinngu. Sagittal otoliths were embedded in epoxy resin, cross-sectioned for age determination, and imaged for back-calculation (size and age). Back-calculated data in each lake were fit to von Bertalanffy growth models for each life-history variant and compared via analysis of residual sums of squares. Anadromous charr had greater mean size at maturity and experienced a delay in mean age at maturity in comparison with lake-residents. The relationship between size and fecundity or egg diameter did not differ between the two life-history variants. Growth models indicate that the overall growth coefficients of lake-resident and anadromous charr were different in all three studied lakes. The Brody growth coefficient for all lake-resident charr populations was greater than anadromous individuals indicating that maximum length was reached at a rapid rate, resulting in a smaller asymptotic length. Indirect evidence suggests that anadromous and lake-resident charr belong to one reproductive population. Future genetic analysis is necessary to further determine the degree of divergence between the life-history variants. [ABSTRACT FROM AUTHOR]

In the family Salmonidae, lake trout (Salvelinus namaycush) are considered the least tolerant of salt water. There are, however, sporadic reports of lake trout in coastal, brackish habitats in the Canadian Arctic. Otolith microchemistry analyses conducted on lake trout and Arctic char (Salvelinus alpinus) from four Arctic lakes in the West Kitikmeot region of Nunavut, Canada, revealed that 37 of 135 (27%) lake trout made annual marine migrations. Anadromous lake trout were in significantly better condition (K = 1.17) and had significantly higher C:N ratios (3.71) than resident lake trout (K = 1.05 and C:N = 3.34). Anadromous lake trout also had significantly higher δ15N (mean = 16.4‰), δ13C (mean = –22.3‰), and δ34S (mean = 13.43‰) isotope ratios than resident lake trout (means = 12.84‰, –26.21‰, and 1.93‰ for δ15N, δ13C, and δ34S, respectively); results were similar for Arctic char and agree with results from previous studies. Mean age of first migration for lake trout was 13 years, which was significantly older than that for Arctic char (5 years). This could be a reflection of size-dependent salinity tolerance in lake trout, but further research is required. These are the first detailed scientific data documenting anadromy in lake trout. Dans la famille des Salmonidae, ce sont les touladis (Salvelinus namaycush) qui sont considérés les moins tolérants à l’eau salée. On signale néanmoins de temps à autre la présence de touladis dans les habitats côtiers et saumâtres de l’Arctique canadien. Des analyses microchimiques des otolithes faites sur des touladis et des ombles chevaliers (Salvelinus alpinus) de quatre lacs arctiques dans la région du Kitikmeot occidental au Nunavut, Canada, montrent que 37 de 135 (27 %) touladis avaient fait des migrations annuelles en mer. Les touladis anadromes sont en significativement meilleure condition (K = 1,17) et possèdent un rapport C:N (3,71) relativement plus élevé que les touladis résidants (K = 1,05 et C:N = 3,34). Les touladis anadromes ont aussi des rapports d’isotopes δ15N (moyenne = 16,4 ‰), δ13C (moyenne = –22,3 ‰) et δ34S (moyenne = 13,43 ‰) plus élevés que ceux des touladis résidants (moyennes de 12,84 ‰, –26,21 ‰ et 1,93 ‰ pour respectivement δ15N, δ13C et δ34S); les résultats sont semblables chez les ombles chevaliers et concordent avec ceux des études antérieures. L’âge moyen de la première migration chez le touladi est de 13 ans, ce qui est significativement plus tard que chez l’omble chevalier (5 ans). Cela pourrait refléter une tolérance à la salinité reliée à la taille chez le touladi, mais il faut des recherches supplémentaires sur le sujet. Nos résultats représentent les premières données scientifiques détaillées sur l’anadromie chez le touladi. [ABSTRACT FROM AUTHOR]

Single-spawning (semelparous) anadromous fishes are known to transport contaminants from marine to freshwater habitats, but little research has been conducted on contaminant biotransport by multiple-spawning (iteroparous) anadromous fishes. We examined the effect of iteroparous, anadromous Arctic charr (Salvelinus alpinus) on mercury concentrations ([Hg]) in freshwater biota and compared [Hg] between species and life history types of Arctic charr and lake trout (Salvelinus namaycush). Data from six lakes and one coastal marine area in the Arctic territory of Nunavut, Canada, indicated that 1) lake trout had significantly lower [Hg] in lakes where anadromous Arctic charr were present; 2) [Hg] was significantly lower in recently discovered anadromous lake trout than in resident lake trout; and 3) regardless of life history, Arctic charr had significantly lower [Hg] than lake trout. These differences were explained by fish condition, age-at-size, and C:N. Biomagnification of Hg, measured as log10[Hg]-δ15N slopes, did not differ between lakes with and without anadromous Arctic charr but was significantly higher in freshwater food webs (∼0.2) than in the marine food web (0.08). Some biomagnification estimates were affected by correction for fish age and size. In contrast to semelparous anadromous species, biotransport of Hg by anadromous Arctic charr appears to be offset by increased growth of freshwater fishes. [ABSTRACT FROM AUTHOR]

Gallagher CP, Dick TA. Trophic structure of a landlocked Arctic char Salvelinus alpinus population from southern Baffin Island, Canada. Ecology of Freshwater Fish 2010: 19: 39–50. © 2009 John Wiley & Sons A/S Stable isotopes, diet and parasites were used to investigate the trophic structure of landlocked Arctic char ( Salvelinus alpinus) from a small Canadian Arctic lake. Two trophic levels of char were identified. The lower trophic level comprised smaller char that consumed mainly invertebrates and harboured low numbers of the cestode plerocercoid Diphyllobothrium spp. while the higher trophic level char were larger, mainly piscivorous and had high numbers of plerocercoids. Procercoids of Diphyllobothrium spp. in copepods are eaten by char where the parasite then differentiates into a plerocercoid. Plerocercoids from smaller fish are transmitted to larger fish by piscivory where they encyst again as plerocercoids until the fish is eaten by a gull. These plerocercoids are a good indicator of trophic level as their numbers accumulate over time in larger fish. The three variables together provided a better resolution of trophic structure than applied separately. For example, plerocercoid numbers plus diet were better predictors of trophic status than stable isotopes in 4–7 year olds, but for char ≥8 years all three variables were complementary. Some char (≥10 years old) were placed in the lower trophic level based on their stable isotope values and had low Diphyllobothrium spp. abundance but were piscivorous and/or cannibalistic. The absence of sexually mature char in the higher trophic group was associated with high numbers of Diphyllobothrium spp. plerocercoids. [ABSTRACT FROM AUTHOR]

Among-lake variation in mercury (Hg) concentrations in landlocked Arctic char was examined in 27 char populations from remote lakes across the Canadian Arctic. A total of 520 landlocked Arctic char were collected from 27 lakes, as well as sediments and surface water from a subset of lakes in 1999, 2002, and 2005 to 2007. Size, length, age, and trophic position (δ15N) of individual char were determined and relationships with total Hg (THg) concentrations investigated, to identify a common covariate for adjustment using analysis of covariance (ANCOVA). A subset of 216 char from 24 populations was used for spatial comparison, after length-adjustment. The influence of trophic position and food web length and abiotic characteristics such as location, geomorphology, lake area, catchment area, catchment-to-lake area ratio of the lakes on adjusted THg concentrations in char muscle tissue were then evaluated. Arctic char from Amituk Lake (Cornwallis Island) had the highest Hg concentrations (1.31 µg/g wet wt), while Tessisoak Lake (Labrador, 0.07 µg/g wet wt) had the lowest. Concentrations of THg were positively correlated with size, δ15N, and age, respectively, in 88, 71, and 58% of 24 char populations. Length and δ15N were correlated in 67% of 24 char populations. Food chain length did not explain the differences in length-adjusted THg concentrations in char. No relationships between adjusted THg concentrations in char and latitude or longitude were found, however, THg concentrations in char showed a positive correlation with catchment-to-lake area ratio. Furthermore, we conclude that inputs from the surrounding environment may influence THg concentrations, and will ultimately affect THg concentrations in char as a result of predicted climate-driven changes that may occur in Arctic lake watersheds. Environ. Toxicol. Chem. 2010;29:633–643. © 2009 SETAC [ABSTRACT FROM AUTHOR]

Concentrations of mercury (Hg) have increased slowly in landlocked Arctic char over a 10- to 15-year period in the Arctic. Fluxes of Hg to sediments also show increases in most Arctic lakes. Correlation of Hg with trophic level (TL) was used to investigate and compare biomagnification of Hg in food webs from lakes in the Canadian Arctic sampled from 2002 to 2007. Concentrations of Hg (total Hg and methylmercury [MeHg]) in food webs were compared across longitudinal and latitudinal gradients in relation to δ13C and δ15N in periphyton, zooplankton, benthic invertebrates, and Arctic char of varying size-classes. Trophic magnification factors (TMFs) were calculated for the food web in each lake and related to available physical and chemical characteristics of the lakes. The relative content of MeHg increased with trophic level from 4.3 to 12.2% in periphyton, 41 to 79% in zooplankton, 59 to 72% in insects, and 74 to 100% in juvenile and adult char. The δ13C signatures of adult char indicated coupling with benthic invertebrates. Cannibalism among char lengthened the food chain. Biomagnification was confirmed in all 18 lakes, with TMFs ranging from 3.5 ± 1.1 to 64.3 ± 0.8. Results indicate that TMFs and food chain length (FCL) are key factors in explaining interlake variability in biomagnification of [Hg] among different lakes. Environ. Toxicol. Chem. 2010;29:621–632. © 2009 SETAC [ABSTRACT FROM AUTHOR]

Data describing Arctic char Salvelinus alpinus were collected in 2002 and 2004 and compared with historical data collected over the past 60 years from the Sylvia Grinnell River, Nunavut, Canada, to determine population status. The goal of the study was to provide information that could be used to manage the stock. Current subsistence harvest was estimated based on data collected from gillnetting, angling, and snagging. The Arctic char subsistence harvest was estimated at 8,364 kg in 2002 and 7,956 kg in 2004. The current population remains well below historic levels, but it has improved since 1976-1977. The improved status of the stock is based on increased length at age, increased mean weight, longer and older fish, decreased mortality rate, and improved catch indices from experimental gill nets and angling. Future benchmarks useful for evaluating the population's status include (1) proportion of females that have reached reproductive age, (2) proportion of older and longer fish, (3) mortality rate, and (4) catch per angler-hour. The fishery should be monitored by enumerating the harvest, quantifying fishing effort from all gear types, and recording biological data. Experimental gill nets should be periodically used to obtain biological data for comparison with the 2002 and 2004 data. Snagging should he prohibited since most young Arctic char (<200-300 mm) are injured and are not utilized by the fishery, and it is impossible to estimate the number of Arctic char larger than 200 mm that are struck and lost instead of landed. We recommend (1) closing all fishing at the base of the falls and at least 500 m into the estuary, (2) limiting gill-net mesh size to no less than 114 mm, 13) implementing benchmarks to evaluate population status, (4) obtaining an estimate of the population size, and (5) determining the exploitation rate. [ABSTRACT FROM AUTHOR]

The presence of two morphotypes of Arctic charr Salvelinus alpinus was confirmed via morphological variation and otolith strontium (Sr) within three open-lake systems of southern Baffin Island, Nunavut, Canada: Qinngu (LH001), Iqalugaarjuit Lake (PG082) and Qasigiat (PG015). Analysis of otolith Sr indicates that a component of each S. alpinus population within lakes LH001 and PG082 is migratory (large–maturing S. alpinus), whereas another component is lake-resident (small–maturing S. alpinus). Alternatively, small and large maturing S. alpinus may both inhabit tidal habitats during their lifetime in lake PG015. Three morphological characters were identified by principal factor analysis (PFA) as characters that were different between maturity groups for all lakes studied: eye diameter, pectoral fin length and pelvic fin length. As well, upper jaw length (LH001 and PG082) and fork depth (PG015) were identified in PFA as traits that differed between morphs. Univariate tests of morphological characters identified by PFA demonstrated maturity group differences with the exception of eye diameter in Lake PG015 and upper jaw length and pelvic fin length in lake LH001. No difference was found in the MANOVA test of upper and lower gill raker number between small–maturing and undeveloped fish within all lakes studied. Clear morphological variation observed between small–maturing and undeveloped fish in all three lakes of the study suggests ecological niche separation between morphotypes. This is the first documented case of lake-resident S. alpinus use of the tidal habitat in the presence of a migratory large–maturing morphotype. [ABSTRACT FROM AUTHOR]

Acoustic technologies were applied to describe how landlocked Arctic char from Iqalugaajuruluit Lake, Baffin Island, interact with its lacustrine habitat. Acoustic data from the lake bottom was collected using sonar equipment and substrate types were verified with benthic grabs and mapped in a geographic information system. Arctic char movements during the open water period were recorded from char fitted with acoustic tags. The distribution of the tagged Arctic char in Iqalugaajuruluit Lake was dependent on fish size and related to abiotic factors such as depth, substrate type and depth/temperature, temporally. The volume of water with temperatures below 6 °C during the open water period may be a limiting factor for large char (>400 mm) in small Arctic lakes. The large piscivorous char are found most often in the deepest water over soft substrates and the smaller char which feed on varying proportions of invertebrates and fish were found most often over the more complex substrates such as boulders, pebbles and gravel. [ABSTRACT FROM AUTHOR]

Arctic char (Salvelinus alpinus L.), the top predator in High Arctic lakes, often is used as a bioindicator of Hg contamination in Arctic aquatic ecosystems. The present study investigated effects of trophic position, size, and age of Arctic char in Lake Hazen, the largest lake in the Canadian High Arctic (81°50'N, 70°25'W), on Hg bioaccumulation. In addition, several essential (Se, K) and nonessential elements (Tl, Cs) in char muscle tissue were examined to compare their behavior to that of Hg. Trophic position of Arctic char was identified by stable isotope (δ15N) signature. Temporal trends of Hg from seven sampling campaigns over a 16-year period (1990-2006) were investigated for the overall data and for one trophic class. Concentrations of Hg were not correlated with age but were positively related to fork length and trophic position. Large char with greater δ15N signatures (>12‰) had larger Hg concentrations (0.09-1.63 μg/g wet wt) than small char with smaller δ15N signatures (<12δ15, 0.03-0.32 μg/g wet wt), indicating that Hg concentrations increased with trophic position. Nonessential Cs and Tl showed relationships to age, length, and trophic position similar to those of Hg, indicating their potential to bioaccumulate and biomagnify. Essential Se and K did not show these relationships. Concentrations of Hg were adjusted using δ15N, leading to less within-year variability and a more consistent temporal trend. The δ15N-adjusted trend showed no decline of Hg in Arctic char from Lake Hazen (1990-2006) in the overall data set and in the small morphotype. Trends for the same period before the adjustment were not significant for the overall data set, but a slight decrease was apparent in the small morphotype. The results confirm the need to consider trophic position and fish size when monitoring temporal trends of Hg, particularly for species... [ABSTRACT FROM AUTHOR]

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 4–32 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. [ABSTRACT FROM AUTHOR]