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Identifying how habitat structure influences the spatiotemporal movements of fishes is important for conservation, population assessment, and management purposes. Here, we determined whether acoustically tagged lake trout (Salvelinus namaycush) from a 305 ha lake exhibited homing behaviour and lake basin fidelity over multiple seasons and years. The lake has two distinct deep basins (north and south) connected by a shallower centre basin. Fifteen lake trout captured during the spawning season from both deep basins were tagged and released in the south basin. All translocated north-basin fish quickly returned to the north basin (median = 1.85 days, range = 0.36-4.5 days), apart from one fish that returned 41 days post-release, while none from the south ventured into the north basin during this time. After translocated individuals returned, all fish demonstrated high basin fidelity among years, as >90% of detections were from the same basin fish were captured, while La determination de l'influence de la structure des habitats sur les deplacements spatiotemporels des poissons est importante pour la conservation, l'evaluation des populations et la gestion. Nous avons determine si des truites grises (Salvelinus namaycush) dotees de radio-etiquettes acoustiques dans un lac de 305 ha presentaient un comportement de retour et une fidelite a leur bassin du lac au fil des saisons et des annees. Le lac compte deux bassins profonds distincts (les bassins nord et sud) relies par un bassin central moins profond. Quinze truites grises capturees des deux bassins profonds durant la periode de frai ont ete etiquetees et relachees dans le bassin sud. Tous les poissons issus du bassin nord ainsi deplaces sont vite retournes dans ce bassin (mediane = 1,85 jours, fourchette = 0,36-4,5 jours), sauf un poisson qui y est retourne 41 jours apres le lacher, alors qu'aucun des poissons issus du bassin sud ne sont entres dans le bassin nord durant cette periode. Apres le retour des individus deplaces, tous les poissons ont fait preuve d'une grande fidelite a leur bassin d'une annee a l'autre, plus de 90 % des detections etant relevees dans le bassin oU les poissons avaient ete captures, alors que, Introduction The study of animal movement and behaviour is fundamental to understanding the life history and habitat use of species (Nathan et al. 2008). In fishes, movement types can vary [...]

Shorthorn sculpin (Myoxocephalus scorpius) are among the most numerous consumers in the Arctic nearshore marine habitats. Despite this, little is known about their movement ecology or predator-prey interactions, particularly with Arctic cod (Boreogadus saida), an important forage fish in the Arctic. Using acoustic telemetry, the movements of tagged sculpin and cod were quantified based on specific locations using a Vemco positioning system during open water when both species were present in the near shore. Movement trajectories of sculpin distinguish three unique types: foraging and feeding behaviour and large transiting movements. The relative time of each of these movement types were correlated to biotic (presence of large numbers of acoustically tagged Arctic cod) and abiotic factors (percent ice coverage and temperature). This study provides unique data on the movement, feeding ecology, and behaviour of an abundant Arctic benthic fish that demonstrates similar movement types to temperate fish. However, further study is needed to quantify specifically the trophic interactions of these important fish and impact on food webs in the rapidly changing Arctic. Meme si les chaboisseaux a epines courtes (Myoxocephalus scorpius) figurent parmi les consommateurs les plus nombreux dans les habitats marins littoraux de l'Arctique, les connaissances sur l'ecologie de leurs deplacements et leurs interactions predateurs-proies, particulierement avec la morue polaire (Boreogadus saida), un important poisson-proie dans l'Arctique, sont limitees. En utilisant la telemetrie acoustique, nous avons quantifie, sur la base d'emplacements precis, les deplacements de chaboisseaux et de morues etiquetes a l'aide d'un systeme de positionnement Vemco en periode d'eau libre, quand les deux especes etaient presentes pres des cotes. Les trajectoires de deplacement des chaboisseaux permettent de distinguer trois types de deplacements, soit des deplacements associes au comportement d'approvisionnement et d'alimentation et de grands deplacements de transit. Le moment relatif de chacun de ces types de deplacements a ete correle a des facteurs biotiques (presence d'un grand nombre de morues polaires dotees d'etiquettes acoustiques) et abiotiques (pour cent de couverture de glace et temperature). L'etude fournit des donnees singulieres sur les deplacements, l'ecologie de l'alimentation et le comportement d'un poisson benthique arctique abondant qui presente des types de deplacements semblables a ceux de poissons d'eaux temperees. D'autres travaux sont toutefois necessaires pour quantifier plus particulierement les interactions trophiques de cet important poisson et leur incidence sur les reseaux trophiques dans un milieu arctique en evolution rapide., Introduction The marine ecosystems of the High Arctic are dynamic, with large seasonal changes in light and temperature, which in turn influence the growth and abundance of primary producers (Walsh [...]

Arctic cod (Boreogadus saida) is a schooling fish providing a critical link between lower and upper trophic levels in the Arctic. This study examined foraging of Arctic cod collected from Allen Bay, Cornwallis Island, Canada (~75 N 95 W), during summer 2010 using temporal indicators of diet including stomach content, and carbon ([delta][sup.13]C) and nitrogen ([delta][sup.15]N) stable isotopes of liver and muscle. Foraging at the time of capture reflected sympagic and epi-benthic habitats indicated by the prevalence of cyclopoid and harpacticoid copepods in stomachs, whereas stable isotope data, which provide an estimate of feeding over a longer period, indicated pelagic prey as important. Prey selection of juveniles differed from adults based on stable isotopes, while large adults showed the most separation based on stomach contents, suggesting size-related diet shifts. Compared to studies near Resolute in the 1970s, 1980s, and 1990s, growth and pre-spawning gonadal conditions of Arctic cod have not changed., Introduction Arctic cod (Boreogadus saida) is a critical link structuring energetic pathways in marine ecosystems throughout the Arctic (Bain and Sekerak 1978; Welch et al. 1992). Understanding its role in [...]

This study documents the spatiotemporal variability of riverine uranium contents and fluxes in rivers discharging into the Hudson, James, and Ungava bays (HJUB). Samples retrieved during a monitoring program of the Koksoak, Great Whale, La Grande, and Nelson rivers were analyzed for dissolved uranium concentration [U] and activity ratio ([sup.234]U/[.sup.238]U). Field surveys conducted during baseflow and snowmelt in six other rivers of the HJUB basin provided complementary data. It is estimated that altogether, the studied rivers export 3.4 X [10.sup.5] mol/year of U towards the HJUB, with a discharge weighted average ([sup.234]U/[.sup.238]U) of 1.27. Two main factors appear to control seasonal fluctuations in dissolved U exports from HJUB rivers: snowmelt and anthropogenic flow control. Under natural hydrological regimes, the dilution of U caused by snowmelt does not compensate for the associated increase in discharge, and riverine U fluxes are intensified during springtime. Contrastingly, the timing of riverine U exports is decoupled from hydroclimatic conditions in rivers affected by flowcontrol structures. Despite the seasonal variations in riverine U contents, the sampling profiles carried along two of the monitored rivers reveal that within the study region, sample locality is at least as important as sampling time for evaluating riverine U fluxes. In addition, a compilation of data from North American rivers reveals that spatial variations in riverine U contents seem to respond to a prominent lithological control, as rivers draining sedimentary rocks (with abundant carbonates) tend to present overall higher U contents and lower ([sup.234]U/[.sup.238]U) variability than the rivers of the Canadian Shield. La presente etude documente la variabilite spatiotemporelle des teneurs et des flux en uranium dans les rivieres se dechargeant dans les baies d'Hudson, de James et d'Ungava (BHJU). Des echantillons preleves dans le cadre d'un programme de suivi des rivieres Koksoak, Grande riviere de la Baleine, La Grande et Nelson ont ete analyses pour leurs concentrations en uranium dissous [U] et leurs rapports d'activite ([sup.234]U/[.sup.238]U). Des mesures effectuees en periode d'etiage et de fonte des neiges dans six autres rivieres s' ecoulant vers les BHJU ont fourni des donnees complementaires. Il est estime qu'ensemble, les rivieres etudiees exportent 3,4 X 105 moles d'uranium par annee vers les BHJU, avec un ratio d'activite ([sup.234]U/[.sup.238]U) moyen de 1,27. Deux principaux facteurs semblent controler les fluctuations saisonnieres des flux d'uranium dissous exportes par ces rivieres : la fonte des neiges et le controle anthropogenique des debits. Sous les regimes hydrologiques naturels, la dilution de l' uranium causee par la fonte des neiges ne compense pas pour l' augmentation de debit y etant associee et les flux d'uranium exportes par les rivieres sont intensifies au printemps. Par contre, dans les rivieres affectees par des structures de controle du debit, la saisonnalite des flux d' uranium est dissociee des conditions hydroclimatiques. Des profils d'echantillonnage effectues le long de deux rivieres montrent que dans la region a l'etude, la variabilite spatiale des teneurs en uranium le long des rivieres est au moins aussi importante que la variabilite saisonniere des teneurs en uranium mesurees a leur exutoire. De plus, une compilation de donnees provenant de rivieres de l'Amerique du Nord montre que les variations spatiales observees dans leur contenu en uranium semblent repondre a un controle lithologique : les rivieres drainant des roches sedimentaires (contenant beaucoup de carbonates) tendent a presenter une concentration plus elevee en uranium et une variabilite ([sup.234]U/[sup.238]U) moindre en comparaison aux rivieres du Bouclier canadien., Introduction Disequilibria among U-series isotopes in the hydrosphere are increasingly documented (e.g., see reviews by Osmond and Ivanovitch 1992; Chabaux et al. 2003, 2008; Vigier and Bourdon 2011 and references [...]

We investigated the effects of various levels of dietary 18:2(n-6) (linoleic acid) and 18:3(n-3) ([Alpha]-linolenic acid) on the growth, feeding, body composition and metabolism of polyunsaturated fatty acids in liver and muscle of Arctic charr. Fish were fed 8 or 12 casein-based semipurified diets in two separate experiments for 12 or 14 wk, respectively. Low levels of dietary 18:2(n-6) and 18:3(n-3) supplemented with pure methyl esters or linseed (flax) oil had an additive effect on fish growth. For each 100 g of diet, the addition of 1.6-1.7 g of 18:3(n-3) and 2.6 g of 18:2(n-6) led to significantly lower fish growth compared with the treatment diets with lower amounts of 18:2(n-6). Whereas 18:2(n-6) was converted to 20:4(n-6) and 22:5(n-6) in the absence or presence of dietary 18:3(n-3), the dominant product of 18:3(n-3) conversion was consistently 22:6(n-3). High levels of dietary 18:3(n-3) markedly inhibited the conversion of 18:2(n-6), whereas the inhibition of dietary 18:2(n-6) on 18:3(n-3) conversion was noted only when the ratio of dietary 18:2(n-6) to 18:3(n-3) changed from 1.0 to 1.5. Feeding diets rich in 18:3(n-3) led to a marked accumulation of 18:3(n-3) and 18:4(n-3) in fish muscle but a negligible change in 20:5(n-3) and 22:6(n-3), regardless of the level of 18:3(n-3) in the diets.

Cases of human diphyllobothriasis have been reported worldwide. Only 1 case in Brazil was diagnosed by our institution from January 1998 to December 2003. By comparison, 18 cases were diagnosed [...]