Range Extension of Bull Trout, Salvelinus confluentus, to the Central Northwest Territories, with Notes on Identification and Distribution of Dolly Varden, Salvelinus malma, in the Western Canadian Arctic

The presence of bull trout (Salvelinus confluentus) is reported from four locations in the Sahtu Settlement Area of the Northwest Territories centered about 64°30'N and 125°00'W. These reports extend the geographical range of this species approximately 500 km north of the previous northernmost published localities in the southern Northwest Territories (~61°N, 125°W, Prairie Creek, Liard River drainage). The identity of these char is confirmed using quantitative criteria in a linear discriminant function from the literature shown to be 100% effective in distinguishing bull trout from Dolly Varden (S. malma). Regular captures of these fish at one location over several years indicate that these records likely represent established populations and not extralimital occurrences. We hypothesize that bull trout are more extensively distributed in high-gradient streams and rivers of the south-central Mackenzie River valley and likely also occur north of this area. Only limited scientific work has been done in the area, and data on taxonomy and distributions of species are generally lacking. In much of the previous literature, reports of char (other than lake trout, S. namaycush) have identified the fish as Dolly Varden or arctic char (S. alpinus). These identifications are suspect, and care must be taken when interpreting such literature. The presence and vulnerability of bull trout present significant challenges for their conservation and management in this area.On a rapporté la présence de l'omble à tête plate (Salvelinus confluentus) à quatre endroits de l'établissement du Sahtu (Territoires du Nord-Ouest), dont la position est environ 64° 30' de lat. N. et 125° 00' de long. O. Ces rapports prolongent l'habitat de cette espèce d'environ 500 km au nord des lieux les plus septentrionaux mentionnés précédemment dans la documentation, lieux situés dans la partie sud des Territoires du Nord-Ouest (~ 61° de lat. N., 125° de long. O., bassin de la Liard). L'identité de ces ombles est confirmée grâce à l'utilisation de critères quantitatifs dans une fonction discriminante linéaire qui a été prouvée 100 p. cent efficace pour établir la distinction entre omble à tête plate et Dolly Varden (S. malma). Les prises régulières de ce poisson à un endroit au cours de plusieurs années révèlent que ces données représentent probablement des populations établies et non des occurrences hors limites. Nous émettons l'hypothèse que la distribution de l'omble à tête plate est plus large dans les ruisseaux et rivières ayant une pente à forte déclivité situés dans le centre-sud de la vallée du Mackenzie, et qu'on le trouve probablement aussi au nord de cette région. Les travaux scientifiques effectués dans la région sont d'une envergure limitée, et les données sur la classification et la distribution des espèces sont dans l'ensemble inexistantes. Dans un grand nombre de documents publiés, les rapports concernant les ombles (autres que le touladi, S. namaycush) ont identifié le poisson comme étant le Dolly Varden ou l'omble chevalier (S. alpinus). Ces identifications sont douteuses et il faut interpréter cette documentation avec prudence. La présence et la vulnérabilité de l'omble à tête plate présentent d'importants défis quant à la préservation et à la gestion de l'espèce à l'intérieur de cette zone

First Records of Sockeye (Oncorhynchus nerka) and Pink Salmon (O. gorbuscha) from Banks Island and Other Records of Pacific Salmon in Northwest Territories, Canada

Eight sexually mature sockeye (Oncorhynchus nerka) and one sexually mature pink salmon (O. gorbuscha) were captured in the subsistence fishery in the Sachs River estuary at Sachs Harbour, Banks Island, Northwest Territories (NT) in August 1993. We also report a first record for coho salmon (O. kisutch) in Great Bear Lake, NT. These capture locations are well outside the known distributions for the species. A pink salmon captured in the West Channel, Mackenzie River near Aklavik, NT, and a chum salmon (O. keta) from Cache Creek [Little Fish Creek], NT, also represent new capture locations within the distribution of the species.En août 1993, on a capturé huit saumons sockeye (Oncorhynchus nerka) adultes et un saumon rose (O. gorbuscha) adulte dans la pêcherie de subsistance située dans l'estuaire de la rivière Sachs, à Sachs Harbour, dans l'île Banks (Territoires du Nord-Ouest). On signale également une première observation du saumon coho (O. kisutch) dans le Grand lac de l'Ours (T.N-O.) Ces lieux de capture sont nettement à l'extérieur des aires de distribution connues pour ces espèces. Un saumon rose capturé dans le Chenal occidental du Mackenzie près d'Aklavik (T.N.-O.), et un saumon kéta (O. keta) provenant de Cache Creek [Little Fish Creek] (T.N.-O.) signalent aussi de nouveaux sites de capture à l'intérieur de l'aire de distribution de ces espèces

Benthic-pelagic trophic coupling in an Arctic marine food web along vertical water mass and organic matter gradients

Source at: http://doi.org/10.3354/meps12582Understanding drivers of benthic-pelagic coupling in Arctic marine ecosystems is key to identifying benthic areas that may be sensitive to climate-driven changes in hydrography and surface production. We coupled algal biomass and sedimentary characteristics with stable isotope data for 113 fishes and invertebrates in the Canadian Beaufort Sea and Amundsen Gulf to examine how trophic structure was influenced by the vertical water mass structure and organic matter input regimes, from 20 to 1000 m depths. Indices of community-level trophic diversity (isotopic niche size, 13C enrichment relative to a pelagic baseline, and δ13C isotopic range) increased from west to east, coincident with the use of more diverse dietary carbon sources among benthic functional groups. Data suggested benthic-pelagic trophic coupling was strongest in the western study region where pelagic sinking flux is relatively high, intermediate in the central region dominated by riverine inputs of terrestrial organic matter, and weakest in the east where strong pelagic grazing is known to limit sinking flux. Differences in δ13C between pelagic and benthic functional groups (up to 5.7 ‰) increased from west to east, and from the nearshore shelf to the upper slope. On the upper slope, much of the sinking organic matter may be intercepted in the water column, and dynamic hydrography likely diversifies available food sources. In waters > 750 m, there were no clear trends in benthic-pelagic coupling or community-level trophic diversity. This study represents the first description of fish and invertebrate food web structure > 200 m in the Canadian Beaufort Sea

Evidence for Non-Anadromous Behaviour of Arctic Charr (Salvelinus alpinus) from Lake Hazen, Ellesmere Island, Northwest Territories, Canada, Based on Scanning Proton Microprobe Analysis of Otolith Strontium Distribution

Scanning proton microprobe analysis was used to determine the distribution of strontium (Sr) in otoliths from arctic charr (Salvelinus alpinus) of known non-anadromous, known anadromous, and unknown life histories. Strontium concentration patterns in otoliths of known non-anadromous charr were low and relatively flat (with little variation) from the core area to the outermost edge of the otolith, while patterns for known anadromous charr were characterized by a similar low, flat region for the first several years of life, followed by marked oscillatory increases and decreases in Sr content for the duration of the fish's life. Small and large forms of Lake Hazen charr of unknown life histories exhibited Sr profiles that were similar to those of the known non-anadromous charr, which strongly suggest that Lake Hazen charr are non-anadromous. These results indicate that Lake Hazen is a "closed" system with energy cycling primarily within the system; this conclusion suggests that a conservative approach would be appropriate for the management of the Lake Hazen charr population.À l'aide d'une sonde protonique à balayage, on a procédé à une analyse afin de déterminer la répartition du strontium (Sr) dans des otolithes prélevés sur des ombles chevaliers (Salvelinus alpinus) ayant eu soit un cycle biologique non anadrome connu, soit un cycle anadrome connu ou un cycle inconnu. Les courbes de concentration en strontium dans les otolithes d'ombles reconnus comme non anadromes étaient faibles et relativement uniformes (montrant peu de fluctuations) en allant du centre de l'otolithe vers la périphérie, tandis que les courbes relatives aux ombles reconnus comme anadromes se caractérisaient par une zone de concentrations faibles et uniformes pour plusieurs des premières années de vie, suivie par des oscillations à la hausse et à la baisse très nettes quant au contenu en Sr pour la durée de vie du poisson. De gros et de petits spécimens d'ombles au cycle biologique inconnu, trouvés dans le lac Hazen, affichaient des profils de Sr semblables à ceux des ombles reconnus comme non anadromes, ce qui suggère fortement que l'omble du lac Hazen est non anadrome. Ces résultats révèlent que le lac Hazen est un système où l'énergie circule surtout en circuit «fermé». Cette conclusion suggère qu'il faudrait adopter une approche prudente quant à la gestion de la population d'ombles du lac Hazen

Relationships between depth and δ15N of Arctic benthos vary among regions and trophic functional groups

The final publication is available at Elsevier via http://dx.doi.org/10.1016/j.dsr.2018.03.010 © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license https://creativecommons.org/licenses/by-nc-nd/4.0/Stable isotope ratios of nitrogen (δ15N) of benthic primary consumers are often significantly related to water depth. This relationship is commonly attributed to preferential uptake of 14N from sinking particulate organic matter (POM) by microbes, and suggests that relationships between δ15N and water depth may be affected by local POM sources and flux dynamics. We examined the relationships between δ15N and water depth (20–500 m) for six trophic functional groups using a mixed effects modelling approach, and compared relationships between two contiguous Arctic marine ecosystems with different POM sources and sinking export dynamics: the Canadian Beaufort Sea and Amundsen Gulf. We demonstrate for the first time in the Arctic that δ15N values of mobile epifaunal carnivores increased as a function of depth when considered separately from benthopelagic and infaunal carnivores, which contrarily did not exhibit increasing δ15N with depth. The δ15N of suspension/filter feeders, infaunal deposit feeders and bulk sediment also increased with water depth, and the slopes of the relationships were steeper in the Amundsen Gulf than in the Beaufort Sea. We propose that regional differences in slopes reflect differences in POM sources exported to the benthos. In the Beaufort Sea, terrestrial POM discharged from the Mackenzie River quantitatively dominates the sedimentary organic matter across the continental shelf and slope, dampening change in δ15N of benthic POM with depth. In the Amundsen Gulf, we attribute a faster rate of change in δ15N of POM with increasing depth to larger contributions of marine-derived POM to the benthic sedimentary pool, which had likely undergone extensive biological transformation in the productive offshore pelagic zone. Differences in POM input regimes among regions should be considered when comparing food webs using stable isotopes, as such differences may impact the rate at which consumer δ15N changes with depth.Funding was provided by the Fisheries Joint Management Committee (Inuvik, NWT), Aboriginal Affairs and Northern Development Canada (BREA), Natural Resources Canada (Environmental Research Fund, Program of Energy Research and Development), internal Fisheries, National Sciences and Engineering Research Council (NSERC) grants to MP and HS, NSERC Alexander Graham Bell CGS D and NSERC Michael Smith Foreign Study Supplement scholarships awarded to AS, and internal support from UiT – The Arctic University of Norway to B

Arctic Sea Ice in Transformation: A Review of Recent Observed Changes and Impacts on Biology and Human Activity

Sea ice in the Arctic is one of the most rapidly changing components of the global climate system. Over the past few decades, summer areal extent has declined over 30, and all months show statistically significant declining trends. New satellite missions and techniques have greatly expanded information on sea ice thickness, but many uncertainties remain in the satellite data and long-term records are sparse. However, thickness observations and other satellite-derived data indicate a 40 decline in thickness, due in large part to the loss of thicker, older ice cover. The changes in sea ice are happening faster than models have projected. With continued increasing temperatures, summer ice-free conditions are likely sometime in the coming decades, though there are substantial uncertainties in the exact timing and high interannual variability will remain as sea ice decreases. The changes in Arctic sea ice are already having an impact on flora and fauna in the Arctic. Some species will face increasing challenges in the future, while new habitat will open up for other species. The changes are also affecting peoples living and working in the Arctic. Native communities are facing challenges to their traditional ways of life, while new opportunities open for shipping, fishing, and natural resource extraction