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Within and among species variation in trophic and habitat shifts with body size can indicate the potential adaptive capacity of species to ecosystem change. In Arctic coastal ecosystems, which experience dramatic seasonal shifts and are undergoing rapid change, quantifying the trophic flexibility of coastal fishes with different migratory tactics has received limited attention. We examined the relationships among body length and condition (Fulton's K, phase angle from Bioelectrical Impedance Analysis) with trophic and habitat shifts (differences in δ15N and δ13C between blood tissues with different turnover rates) of two abundant and culturally important species, anadromous Arctic char (Salvelinus alpinus, n = 38) and sedentary Greenland cod (Gadus ogac, n = 65) during summer in coastal marine waters near Ulukhaktok, Northwest Territories, Canada. Habitat shifts (δ13C) increased with length (i.e., pelagic to benthic-littoral) and crossed-equilibrium (zero) at mid-sizes for both species. Seasonal trophic shifts (δ15N) were generally positive (i.e., increasing trophic level) for Arctic char and negative for Greenland cod. As hypothesised, intra-individual variation in size-based trophic shifts (δ15N-length residuals) increased with length for Arctic char. However, there were no trends with length in Greenland cod. Our findings highlight the importance of flexibility through ontogeny and mobility for Arctic char, whereas Greenland cod were generalist to localized prey and habitat across all sizes. The significant effect of body condition (phase angle) on size-based trophic shifts in Arctic char, and size-based habitat shifts in Greenland cod, highlight the potential trade-offs of contrasting life history strategies and capacity for ontogenetic niche plasticity. [ABSTRACT FROM AUTHOR]

Fish and marine mammals are an important traditional subsistence and cultural resource for residents of Ulukhaktok, a community within the Inuvialuit Settlement Region, Northwest Territories. Community-based harvest surveys were conducted monthly out of Ulukhaktok, between 2004 and 2015, to enumerate fish and marine mammal subsistence harvest. Anadromous Arctic Char (annual average: 3,464 fish), Lake Trout (annual average: 2,114 fish), and Ringed Seals (annual average: 256 seals) continue to be the most abundantly harvested fish and marine mammal species 2004-2015, with landlocked Arctic Char (annual average: 203 fish), whitefish (annual average: 74 fish), cod (annual average: 136 fish), and Bearded Seals (annual average: 8) also reported. Accessibility to harvesting areas and availability of fish and marine mammals were strongly linked to seasonal cycles. Following concerns regarding the population status of Kuujjua River (i.e., Tatik Lake) Arctic Char, and to support the sustainable management of all Arctic Char subsistence and commercial fisheries in the area, the Ulukhaktok Char Working Group (UCWG) was established in 1996. The UCWG implemented a community fishing plan with voluntary management measures and fishery guidelines supported by harvest data provided by monitoring programs. In response to the observed decline in stock status, the UCWG established a voluntary subsistence harvest level of 1,000 fish from Tatik Lake which has not been surpassed in recent years (2003-2015); however, the total number of Kuujjua River Arctic Char harvested is unknown due to the uncertainty regarding contributions to the coastal mixed-stock harvest. Total annual harvest of anadromous Arctic Char from respective management zones 1988-2015 varied as follows: a) between 486 and 6,297 fish in coastal waters; b) between 0 (voluntary community closure) and 4,386 fish from the Kuujjua River; and c) between 0 and 5,502 fish from rivers in Prince Albert Sound. Co-management partners consider all available information collected through harvest surveys, monitoring programs, Indigenous Knowledge and observations, and scientific research to support the adaptive comanagement of these important fish and marine mammal species in a changing climate. [ABSTRACT FROM AUTHOR]

The summer coastal Arctic Char (Salvelinus alpinus) fishery is an important cultural, subsistence, and commercial resource for the community of Ulukhaktok in the Inuvialuit Settlement Region, Northwest Territories. Anadromous Arctic Char are caught while they are feeding along the coast during summer, generally early-July to late-August. A community-based harvest monitoring program was conducted during 1993-1997 and 2011-2015 to collect catchper-unit-effort (CPUE) and biological data from the coastal subsistence fishery. The community has also conducted a small-scale Arctic Char commercial fishery, licensed as a Stage 1 Exploratory Fishery with catch and biological data reporting requirements. Median CPUE in the subsistence fishery ranged from 19.2 to 32.8 Arctic Char/100 m net/24 h, with no trends over time in either sampling period or overall. There was an increase in the length and weight of Arctic Char harvested in the coastal fishery between sampling periods, with the majority of fish between 500 mm and 650 mm, and 1,500 g to 3,000 g in 1993-1997, and between 550 mm and 800 mm and 2,500 g and 5,000 g in 2011-2015. The majority of Arctic Char harvested in the subsistence fishery were between 8 and 13 years. Annual mortality during 2011 to 2015 was relatively stable at a low level (0.17-0.3). In addition to changes in size, there was evidence of increases in growth rate (length-at-age) between 1993-1997 and 2011-2015. Biological data collected from the commercial fishery were similar to those collected from the subsistence fishery although the commercial catch was comprised of a higher proportion of large (= 700 mm) fish which is expected given some differences in gear types. The available information suggests that the populations contributing to the coastal summer fishery are sustainable at present harvest levels. The collection of biological and CPUE data from subsistence and commercial fisheries continues to be a priority for the Ulukhaktok Char Working Group, to support their use of adaptive co-management and enable the sustainable management of their Arctic Char fisheries. Continued monitoring and research, that include both Indigenous Knowledge and scientific methods are required to better understand, characterize, and assess the stocks that contribute to this mixed-stock coastal fishery. [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]

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]

A comparative analysis of the mitochondrial DNA variability in Salvelinus taranetzi (and closely related taxa) from Asia and Salvelinus alpinus erythrinus from the Northwest Territories (NWT), North America, representing the Arctic phylogenetic group of charrs of the genus Salvelinus, has been carried out. The estimated divergence of the combined nucleotide sequences of the mtDNA CoI and Cytb genes and CR region within the discussed phylogroup varies in the range of 0.001–0.003 and does not exceed the intraspecific variability of S. taranetzi. A genealogical analysis confirms the phylogenetic proximity of S. a. erythrinus from NWT and S. taranetzi from Asia. By assuming a common origin of S. taranetzi and S. a. erythrinus, we have shown a significant differentiation between the geographical populations as a result of probable fragmentation of their common ancestor's range. According to the hierarchical analysis of molecular variance (AMOVA), the intergroup component accounts for the major part (83% of variance) of the mtDNA variability (490 bp, CR) with a low genetic diversity within the groups (10%). The region of Anadyr–Kolyma Basin, which determines the heterogeneity of the phylogroups, stands out on a broad geographical scale. [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]

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]