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Arctic fishes are threatened by climatic change and other anthropogenic stressors, yet information on how such changes impact survival remains scarce. Acoustic telemetry has become valuable for studying aspects of fish ecology, including survival, which is invaluable in understanding potential responses to changing conditions. In Cambridge Bay, NU, we have been using acoustic telemetry to study movements and habitat use of the culturally and commercially important Arctic char (Salvelinus alpinus). Here, we combine acoustic telemetry data and Bayesian multistate mark-recapture models to study the survival of Arctic char from 2014 to 2018 in the region in freshwater and marine/estuarine habitats. We found that survival probabilities were high (>0.87) and models considering two environments (freshwater and marine) perform better than those considering three (including estuarine habitats). Furthermore, the survival in fresh water was higher than survival in marine/estuary environments. Overall, the results of this study further our understanding of important demographic parameters (i.e., survival) for Arctic char in the region, which will be useful in refining fishery management plans for the largest commercial fishery for this species in Canada. Key words: acoustic telemetry, Arctic char, Bayesian statistics, mark-recapture models, survival ecology Si les poissons de l'Arctique sont menaces par les changements climatiques et autres facteurs de stress d'origine humaine, l'information sur l'incidence de ces changements sur leur survie demeure rare. La telemetrie acoustique est devenue prisee pour etudier divers aspects de l'ecologie des poissons, notamment la survie, un parametre essentiel pour comprendre les possibles reactions a des conditions changeantes. Nous utilisons la telemetrie acoustique pour etudier les deplacements et l'utilisation d'habitats par les ombles chevaliers (Salvelinus alpinus), une espece d'importance culturelle et commerciale, dans la baie Cambridge (Nunavut). Nous combinons des donnees de telemetrie acoustique et des modeles bayesiens multietats de marquage-recapture afin d'etudier la survie des ombles chevaliers de 2014 a 2018 dans des habitats d'eau douce et marins/estuariens de cette region. Nous relevons que les probabilites de survie sont elevees (>0,87) et que les modeles qui integrent deux types de milieux (d'eau douce et marin) donnent de meilleurs resultats que ceux qui en integrent trois (incluant les habitats estuariens). La survie en eau douce s'avere en outre plus grande que la survie dans les milieux marins/estuariens. Globalement, les resultats de l'etude ameliorent la comprehension de parametres demographiques importants (c.-a-d., la survie) pour l'omble chevalier dans la region, ce qui sera utile pour peaufiner les plans de gestion des ressources pour la plus importante peche commerciale de cette espece au Canada. [Traduit par la Redaction] Mots-cles : telemetrie acoustique, omble chevalier, statistiques bayesiennes, modeles de marquage-recapture, ecologie de la survie, Introduction Climate change in the Canadian Arctic is occurring at some of the fastest rates on Earth (Prowse et al. 2006; Barber et al. 2008; Pithan and Mauritsen 2014). This [...]

Animal interactions are an integral part of a community's function, with influences ranging from the spatiotemporal habitat use of species to population effects to ecosystem management. Numerous non-native species are established or maintained through stocking in freshwater ecosystems with the potential to affect restoration of native species. Using acoustic telemetry, this study quantified the spatiotemporal co-occurrence of the native top-predator lake trout (Salvelinus namaycush) with non-native Chinook salmon (Oncorhynchus tshawytscha) in Lake Ontario over 2.5 years. Core home range overlap was observed during the summer, with depth acting as a mechanism of segregation, but with potential for interactions during vertical exploration. Fine-scale individual pairwise interactions confirmed the home range results. No horizontal overlap was observed during the winter and spring, but confidence was lower due to poor instrument coverage in deeper water, which the two species may frequent in these seasons. These results demonstrate the importance of depth in understanding fish interactions and highlight the usefulness of considering pairwise species interactions for understanding ecosystem community function to resource managers with multiple projects involving both native and non-native species. Les interactions d'animaux font partie integrante de la fonction d'une communaute et influent sur differents aspects allant de l'utilisation spatiotemporelle d'habitats a des effets demographiques, en passant par la gestion des ecosystemes. De nombreuses especes non indigenes sont etablies et maintenues par empoissonnement dans des ecosystemes d'eau douce, ce qui peut avoir une incidence sur le retablissement d'especes indigenes. La presente etude a utilise la telemetrie acoustique pour quantifier la cooccurrence spatiotemporelle d'un predateur de niveau trophique superieur indigene, le touladi (Salvelinus namaycush), et du saumon chinook (Oncorhynchus tshawytscha), non indigene, dans le lac Ontario sur une periode de 2,5 annees. Un chevauchement de leurs domaines vitaux a ete observe durant l'ete, la profondeur agissant comme mecanisme de segregation, des interactions etant toutefois possibles durant l'exploration verticale. Des interactions par paires a petite echelle ont confirme ces resultats relatifs au domaine vital. Aucun chevauchement horizontal n'a ete observe en hiver et au printemps, mais la fiabilite de ces resultats est plus faible en raison d'une couverture d'instruments moins importante dans les eaux plus profondes que les deux especes pourraient frequenter pendant ces saisons. Ces resultats demontrent l'importance de la profondeur pour la comprehension des interactions de poissons et soulignent l'utilite, pour les gestionnaires de ressources voyant a differents projets visant des especes indigenes et non indigenes, d'examiner les interactions d'especes par paires afin de comprendre la fonction ecosystemique de communautes. [Traduit par la Redaction], Introduction Ecosystem function is defined by the structure of its communities, with species interactions being a key component driving complexity (Lang and Benbow 2013). As such, species interactions are an [...]

Conceptually, trophic niche overlap and species abundance can describe the strength and number of interspecific trophic interactions to determine the competitive impact on reintroduced species or other ecosystem changes. We use an example with young-of-year (YOY) Atlantic salmon (Salmo salar) reintroductions to determine whether trophic niche overlaps and abundances limit restoration success. Using seasonal stable isotopes and abundance estimates for invertivorous fishes in three Lake Ontario tributaries, we assessed community isotopic structure, trophic niche overlap, and the impact of the niche overlap by incorporating relative abundance. Brown trout (Salmo trutta) YOY could be a strong competitor with a high trophic niche overlap with Atlantic salmon YOY, but at lower abundances relative to Atlantic salmon there is minimal impact. Stream resident fish communities appeared to partition resources across seasons such that abundant species had low trophic niche overlap to minimize overall competition with Atlantic salmon YOY given available resources, indicating niche complementarity. Through joint consideration of trophic overlap and abundance using our conceptual model, the competitive impact of community composition on a reintroduced species could be assessed. D'un point de vue conceptuel, le chevauchement de niches trophiques et l'abondance d'especes peuvent servir a decrire la force et le nombre des interactions trophiques entre especes dans le but de determiner l'impact concurrentiel sur des especes reintroduites ou d'autres modifications des ecosystemes. Nous utilisons l'exemple de reintroductions de jeunes saumons atlantiques (Salmo salar) de l'annee pour etablir si les chevauchements de niches trophiques et l'abondance limitent le succes du retablissement. En utilisant des analyses d'isotopes stables et des estimations de l'abondance saisonnieres pour des poissons invertivores dans trois affluents du lac Ontario, nous evaluons la structure isotopique des communautes, le chevauchement de niches trophiques et l'impact de ce chevauchement en tenant compte de l'abondance relative. De jeunes truites brunes (Salmo trutta) de l'annee pourraient etre d'importants concurrents dont la niche trophique chevauche fortement celle des jeunes saumons atlantiques de l'annee, mais leur faible abondance relative par rapport a celle des saumons atlantiques en minimise l'impact. Les communautes de poissons residents des cours d'eau semblent faire preuve de partage referentiel des ressources d'une saison a l'autre, de sorte que les niches trophiques des especes abondantes se chevauchent peu afin de minimiser la concurrence globale avec les jeunes saumons atlantiques de l'annee etant donne les ressources disponibles, ce qui indique une complementarite des niches. En considerant le chevauchement trophique et l'abondance ensemble dans notre modele conceptuel, nous sommes en mesure d'evaluer l'impact concurrentiel de la composition des communautes sur une espece reintroduite. [Traduit par la Redaction], Introduction In aquatic systems, stocking fish to supplement wild populations and enhance fisheries occurs globally, and it is important to determine any limitations to stocking success (Minckley 1995; Brown and [...]

Walleye (Sander vitreus) are a sexually dimorphic freshwater piscivore that have long been studied using bioenergetics modeling, yet robust estimates of metabolic rates for use in those models have been lacking. Therefore, we quantified the effects of body mass, water temperature, and sex, on standard metabolic rate (SMR). We estimated SMR across temperatures ranging 0.5–24 °C using intermittent-flow respirometry for male (n = 54) and female (n = 53) walleye raised in hatchery conditions. We found a significant interaction between sex and temperature, whereby males had lower SMR below 16 °C, but increased such that SMR was ∼16% higher than females at 22 °C. The mass-scaling coefficient, b, was similar for both sexes at a value around 1. These estimates are the first to be generated using respirometry for adult walleye and differ slightly from those being used by previous bioenergetics models, which may have underestimated the energetic costs of SMR, and did not include sex-specific estimates for metabolism. [ABSTRACT FROM AUTHOR]

Regulated waterways, interconnected by navigation barriers (locks and dams), are uniquely difficult to manage, given interest in enabling native species connectivity while minimizing invasions. Canada's historic Rideau Canal Waterway, a 202 km navigable route located in eastern Ontario and connected by 24 lockstations, embodies this challenge. The lock(s) and water-control dam that compose each lockstation may respectively offer a connectivity pathway, though to what extent is unclear. We used acoustic telemetry (native largemouth bass (Micropterus nigricans) and northern pike (Esox lucius), and invasive common carp (Cyprinus carpio); n = 224) to evaluate fish connectivity relative to lock operations and environmental data over three years (2019–2021). Thirty-five passages by 23 native fishes were recorded, with 49% of passages through locks. No common carp passages were detected; movements indicate that they favour higher flow areas downstream of dams, regions with no pathway upstream. Most passages were downstream and, of concern to obligate upstream migrators, we found that multi-flight and higher-lift locks appear impassable to upstream movements. Our results suggest that these lockstations limit, but not entirely restrict, connectivity. [ABSTRACT FROM AUTHOR]

Alternative reproductive tactics (ARTs) can generate considerable within-species life history variation but are often overlooked. Here, we use the invasive round goby (Neogobius melanostomus) to address a number of ecological and evolutionary questions about ARTs. Making use of a 12-year, multisite Laurentian Great Lakes data set, we show that the guarder male tactic was twice as common as the sneaker male tactic but that nonreproductive males were the most common morph. The ratio of guarder to sneaker males did not vary spatially despite a wide range of resource densities across sites. Guarders and sneakers spanned similar age ranges, suggesting that the ARTs are nonsequentially expressed. Based on short-term (gut contents) diet analyses, both reproductive tactics consumed fewer types of food and tended to consume fewer items overall when compared with nonreproductive males. Long-term (isotope) diet analyses showed that guarder males fed at a higher trophic level (higher [[delta].sup.15]N) and had a broader isotopic niche. Our results show that ARTs are an important aspect of this invasive species' breeding system and should be accounted for when assessing and managing populations. Si differentes tactiques de reproduction peuvent se traduire par des variations considerables du cycle biologique au sein d'une meme espece, dans bien des cas, elles ne sont pas prises en consideration. Nous utilisons le gobie a taches noires (Neogobius melanostomus), une espece envahissante, pour examiner differentes questions relatives a l'ecologie et Revolution touchant aux differentes tactiques de reproduction. A la lumiere d'un ensemble de donnees de 12 ans couvrant de multiples sites dans la region des Grands Lacs laurentiens, nous demontrons que les males gardiens etaient deux fois plus repandus que les males furtifs, mais que les males non reproducteurs representaient la tactique la plus repandue. Le rapport des males gardiens et furtifs ne variait pas dans l'espace, malgre une grande fourchette de densite des ressources entre les sites. Les fourchettes d'age des males gardiens et furtifs etaient semblables, donnant a penser que les differentes tactiques de reproduction ne s'expriment pas sequentiellement. A la lumiere d'analyses des regimes alimentaires a court terme (contenus stomacaux), les individus adoptant les deux tactiques de reproduction consommaient moins de types d'aliments et avaient tendance a consommer moins d'articles en general que les males non reproducteurs. Des analyses des regimes alimentaires sur le long terme (isotopiques) montrent que les males gardiens s'alimentaient a un niveau trophique plus eleve ([[delta].sup.15]N plus grands) et occupaient une niche isotopique plus large. Nos resultats montrent que l'adoption de differentes tactiques de reproduction est un aspect important du systeme de reproduction de cette espece envahissante qui devrait etre integre a l'evaluation et la gestion des populations. [Traduit par la Redaction], Introduction The round goby (Neogobius melanostomus) is a highly successful invasive species that has established new populations in both Europe and North America (Corkum et al. 2004; Kornis et al. [...]

Aquatic animals are integral to ocean and freshwater ecosystems and their resilience, are depended upon globally for food sustainability, and support coastal communities and Indigenous peoples. However, global aquatic environments are changing profoundly due to anthropogenic actions and environmental change. These changes are altering distributions, movements, and survival of aquatic animals in ways that are not well understood. The Ocean Tracking Network (OTN) is a global partnership that is filling this knowledge gap. OTN Canada, a pan-Canadian (and beyond) research network, was launched in 2010 with visionary funding by the Canadian government. In our introduction to this special issue, we briefly overview how this interdisciplinary network has used state-of-the-art technologies, infrastructure, electronic tags and sensors, and associated cutting-edge research and training programs to better understand changing marine and freshwater dynamics and their impact on ecosystems, resources, and animal ecology. These studies have provided unprecedented insights into animal ecology and resource management at a range of spatial and temporal scales and by interfacing animal movements with novel measures of environment, physiology, disease, genetics-genomics, and anthropogenic stressors. Les animaux aquatiques sont des elements essentiels des ecosystemes oceaniques et d'eau douce et de la resilience de ces systemes, ils assurent la perennite de la disponibilite de nourriture a l'echelle planetaire et supportent des collectivites cotieres et des peuples autochtones. Les milieux aquatiques planetaires font toutefois l'objet de modifications profondes causees par l'activite humaine et des changements environnementaux. L'incidence de ces modifications sur la repartition, les deplacements et la survie des animaux aquatiques n'est pas bien comprise. L'Ocean Tracking Network (OTN) est un partenariat international qui vise a combler ces lacunes dans les connaissances. OTN Canada, un reseau de recherche pancanadien (et au-dela) a ete lance en 2010 grace au financement visionnaire du gouvernement du Canada. Dans notre introduction au present numero special virtuel, nous presentons un bref survol de l'emploi fait par ce reseau interdisciplinaire des plus recentes technologies, infrastructures, des etiquettes et capteurs electroniques et de la recherche et des programmes de formation de pointe associes pour mieux comprendre la dynamique changeante des milieux marins et d'eau douce et son incidence sur les ecosystemes, les ressources et l'ecologie animale. Ces etudes jettent un eclairage sans precedent sur l'ecologie animale et la gestion des ressources a differentes echelles spatiales et temporelles, en reliant les deplacements d'animaux a de nouvelles mesures du milieu, de la physiologie, des maladies, de la genetique-genomique et de facteurs de stress d'origine humaine., Introduction Aquatic animals help meet global food needs, annually contribute billions of dollars in socioeconomic benefits and ecosystem services to society, support coastal communities, and are culturally important, particularly for [...]

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 [...]

Lake sturgeon (Acipenserfulvescens) were once abundantly distributed throughout the Laurentian Great Lakes. However, widespread overharvesting and habitat degradation has diminished their numbers. The lower Niagara River contains one of the few remnant lake sturgeon populations in New York State. This study determined the diet of adult lake sturgeon and quantified their trophic position in a food web dominated by non-native species. Stomach content analysis assessed recent diet, and stable isotope analysis ([delta][sup.15]N and [delta][sup.13]C) of blood and fin tissue quantified trophic position and carbon source over varying time scales. Two non-native species dominated the diet of lake sturgeon--the amphipod Echinogammarus ischnus (62% by number) and the round goby (Neogobius melanostomus) (44% by mass). Stable isotope analysis revealed that round goby was the primary contributor to the long-term (i.e., fin) average diet, whereas short-term (i.e., blood) diet was more diverse. In contrast with findings from other systems, we found that adult lake sturgeon in the lower Niagara River were primarily piscivorous, actively targeting live fish prey. The recovery of this population is potentially supported by the high availability of energetically rich but non- native food resources.Les esturgeons jaunes (Acipenser fulvescens) ont deja ete abondants a la grandeur des Grands Lacs laurentiens. La surexploitation et la degradation des habitats repandues ont toutefois reduit leur nombre. Le cours inferieur de la riviere Niagara contient une des rares populations restantes d'esturgeons jaunes dans l'Etat de New York. L'etude a determine le regime alimentaire d'esturgeons jaunes adultes et quantifie leur position trophique dans un reseau trophique domine par des especes non indigenes. L'analyse de contenus stomacaux a permis d'evaluer le regime alimentaire recent et l'analyse d'isotopes stables (S15n et [delta][sup.13]C) de sang et de tissus de nageoire a permis de quantifier la position trophique et les sources de carbone a differentes echelles temporelles. Deux especes non indigenes etaient dominantes dans le regime alimentaire des esturgeons jaunes, soit l'amphipode Echinogammarus ischnus (62 % en nombre) et le gobie a taches noires (Neogobius melanostomus) (44 % en poids). Les isotopes stables ont revele que le gobie a taches noires etait le principal element du regime alimentaire moyen sur le long terme (c.-a-d. nageoires), alors que, a court terme (c.-a-d. sang), le regime alimentaire etait plus varie. Contrairement aux constatations pour d'autres systemes, les esturgeons jaunes adultes dans le cours inferieur de la riviere Niagara etaient principalement piscivores, ciblant activement des poissons vivants comme proies. Le retablissement de cette population est potentiellement soutenu par la grande disponibilite de ressources alimentaires riche en energie, mais non indigenes. [Traduit par la Redaction], IntroductionLake sturgeon are large, long-lived benthic fish whose range-wide abundance has declined precipitously over the past century, resulting in their designation as a species of conservation concern in many US [...]

The use of baselines in stable isotope studies to interpret food web structure is essential, but baseline isotope values are often assumed to be spatially homogeneous, even in large aquatic ecosystems. To test this assumption in large lakes, we quantified spatial variation in δ13C, δ15N (deposit‐feeding Oligochaeta and filter‐feeding Dreissena spp.), and δ34S (Dreissena spp. only) and density in Lake Erie between 2014 and 2016. Lake Erie's three distinct basins differ in size, bathymetry, and nutrient loading, making it an excellent system for exploring spatial variation in stable isotopes of baseline organisms. Dreissena spp. densities were highest in the western and lowest in the seasonally hypoxic central basin, while Oligochaeta densities were relatively consistent throughout Lake Erie. Values of δ13C, δ15N, and δ34S exhibited distinct spatial trends that were not related to population densities but followed the west to east direction of water flow within the lake. For both taxa, δ13C was lower in the deeper, oligotrophic east basin than the shallow, mesotrophic west basin, and δ15N and δ34S increased from west to east. Spatial patterns of low δ34S in Dreissena spp. in the western and central basins were likely related to hypoxia, whereas patterns of δ15N in both taxa were probably related to the greater influence of agricultural land uses in the western basin. Spatial trends of stable isotopes in large lake zoobenthos are driven by complex interactions of environmental gradients, which could introduce bias in evaluations of trophic structures within aquatic ecosystems that use stable isotopes. [ABSTRACT FROM AUTHOR]

The Great Lakes Acoustic Telemetry Observation System (GLATOS), organized in 2012, aims to advance and improve conservation and management of Great Lakes fishes by providing information on behavior, habitat use, and population dynamics. GLATOS faced challenges during establishment, including a funding agency-imposed urgency to initiate projects, a lack of telemetry expertise, and managing a flood of data. GLATOS now connects 190+ investigators, provides project consultation, maintains a web-based data portal, contributes data to Ocean Tracking Network's global database, loans equipment, and promotes science transfer to managers. The GLATOS database currently has 50+ projects, 39 species tagged, 8000+ fish released, and 150+ million tag detections. Lessons learned include (1) seek advice from others experienced in telemetry; (2) organize networks prior to when shared data is urgently needed; (3) establish a data management system so that all receivers can contribute to every project; (4) hold annual meetings to foster relationships; (5) involve fish managers to ensure relevancy; and (6) staff require full-time commitment to lead and coordinate projects and to analyze data and publish results. Le systeme d'observation par telemetrie acoustique des Grands Lacs (GLATOS), mis sur pied en 2012, vise a faire avancer et a ameliorer la conservation et la gestion des poissons des Grands Lacs en fournissant de l'information sur les comportements, l'utilisation des habitats et la dynamique des populations. GLATOS a fait face a differents defis durant son etablissement, dont l'urgence d'entreprendre des projets imposee par les organismes de financement, un manque d'expertise en telemetrie et la gestion d'une quantite massive de donnees. GLATOS relie aujourd'hui plus de 190 chercheurs, fournit des conseils sur des projets, maintient un portail de donnees sur le web, fournit des donnees a la base de donnees planetaire de l'Ocean Tracking Network, prete du materiel et fait la promotion du transfert des connaissances scientifiques aux gestionnaires. La base de donnees de GLATOS compte actuellement plus de 50 projets, 39 especes etiquetees, plus de 8000 poissons relaches et plus de 150 millions de detections d'etiquettes. Les lemons tirees comprennent l'importance (1) de demander les avis et conseils d'autres intervenants avec de l'experience en telemetrie, (2) d'organiser les reseaux avant que ne se presentent des besoins urgents d'echange des donnees, (3) d'etablir un systeme de gestion des donnees pour faire en sorte que tous les recepteurs puissent contribuer a tous les projets, (4) d'organiser des reunions annuelles pour renforcer les liens, (5) d'inclure les gestionnaires des peches pour assurer la pertinence des projets et (6) de prevoir le personnel a temps plein necessaire pour assurer la direction et la coordination des projets, l'analyse des donnees et la publication des resultats. [Traduit par la Redaction], Introduction Acoustic telemetry has become increasingly popular for investigating behavior, habitat preferences, and population dynamics of native and invasive fish in fresh and marine waters (e.g., Hussey et al. 2015; [...]

Bluegill (Lepomis macrochirus) and pumpkinseed (Lepomis gibbosus) sunfish function as a trophic link between invertebrates and piscivores in temperate freshwater food webs, but little is known about their movement in large-scale riverine ecosystems. To address this, pumpkinseed and bluegill were implanted with acoustic transmitters and monitored for 5 months (June to November 2015) within a 0.39 [km.sup.2] acoustic array in the Detroit River. Residence index analysis revealed site fidelity of sunfish to the side of the river they were tagged and a lack of movement across a shipping channel. Bluegill were more active at night and pumpkinseed more active during daylight hours, possibly partitioning resources on a temporal basis, unlike in smaller lakes where the species partition the littoral and pelagic habitats. Pumpkinseed presence was positively correlated with water temperature and level, whereas bluegill presence was not related to any environmental parameters examined. This study demonstrates that anthropogenic alterations (e.g., channelization) influence the movement and distribution of fishes and that fish behaviour in a large river ecosystem can differ from smaller temperate lakes. Si le crapet arlequin (Lepomis macrochirus) et le crapet-soleil (Lepomis gibbosus) tiennent lieu de lien trophique entre invertebres et piscivores dans les reseaux trophiques de milieux d'eau douce temperes, les connaissances sur leurs deplacements dans les ecosystemes de grande envergure sont limitees. Pour examiner cette question, des crapets arlequins et des crapets-soleil ont ete dotes d'emetteurs acoustiques, puis suivis pendant 5 mois (de juin a novembre 2015) dans un reseau acoustique de 0,39 [km.sup.2] dans la riviere Detroit. L'analyse de l'indice de residence revele une fidelite au site des crapets du cote de la riviere ou ils ont ete marques et l'absence de deplacements traversant un chenal de navigation. Les crapets arlequins etaient plus actifs la nuit et les crapets-soleil, le jour, ce qui pourrait refleter un partage des ressources sur une base temporelle, contrairement a ce qui est observe dans de plus petits lacs ou les especes se divisent les habitats littoraux et pelagiques. La presence de crapets-soleil etait positivement correlee a la temperature et au niveau de l'eau, alors que celle de crapets arlequins n'etait reliee a aucun des parametres du milieu examines. L'etude montre que les modifications d'origine humaine, telle que la canalisation, influencent les deplacements et la repartition de poissons et que le comportement des poissons dans l'ecosysteme d'une grande riviere peut etre different de celui qui est observe dans les petits lacs temperes. [Traduit par la Redaction], Introduction Fish movements and distributions form the basis of the structure and functioning of aquatic ecosystems (Hussey et al. 2015). As a source of substantial energy subsidies to food webs, [...]

We summarize geographical patterns in ringed seal (Pusa hispida (Schreber, 1775)) body length and girth growth using 3012 samples collected by Inuit hunters in the eastern Canadian Arctic from 1990 to 2016. Spatial structure was detected using cluster analysis of environmental variables separating a northern region in the eastern Canadian High Arctic and a southern region in Hudson Bay. The north was characterized by more fast ice, multiyear ice, greater snow depth, colder temperatures, and greater sea-ice concentration in the spring seal breeding season. Hierarchical Bayesian models described length and axillary girth growth of northern seals as slower than in the south, reaching asymptotic size 5-7 years later. Northern females were larger than males (asymptotic length of 149 versus 140 cm, respectively) and both were larger than southern seals (males and females 126 cm). We conclude that environmental variation was best represented by regions rather than latitude, regional body size differences were driven by differential growth rates, and northern ringed seals may be characterized by reverse sexual size dimorphism. Key words: asymptotic body size, Brody growth rate, Nunavut, phocids, pinnipeds, Pusa hispida, ringed seal, sea ice, sexual size dimorphism, snow, temperature. Nous décrivons les motifs de répartition géographique de la croissance de la longueur du corps et du périmètre thoracique de phoques annelés (Pusa hispida (Schreber, 1775)) en utilisant 3012 spécimens prélevés par des chasseurs inuits dans l'est de l'Arctique canadien de 1990 à 2016. Une structure spatiale est décelée en utilisant l'analyse typologique de variables environnementales, qui distingue une région septentrionale dans l'est de l'Extrême-Arctique canadien d'une région méridionale dans la baie d'Hudson. Le Nord est caractérisé plus de glace fixée et de glace pluriannuelle, de plus grandes épaisseurs de neige, des températures plus froides et une plus grande concentration de glace marine durant la période de reproduction printanière des phoques. Des modeles bayésiens hiérarchiques décrivent la croissance de la longueur et du périmètre axillaire des phoques du Nord comme étant plus lente que celles des phoques du Sud, atteignant des valeurs asymptotiques5 à 7 ans plus tard. Les femelles du Nord sont plus grandes que les mâles du Nord (longueur asymptotique de 149 cm contre 140 cm, respectivement), les deux étant plus grands que les phoques du Sud (126 cm pour les mâles et les femelles). Nous en concluons que les régions reflètent mieux les variations environnementales que la latitude, que les différences régionales sur le plan de la taille du corps sont le fait de taux de croissance différents et que les phoques annelés du nord pourraient présenter un dimorphisme sexuel inversé de la taille. [Traduit par la Rédaction] Mots-clés: taille asymptotique du corps, taux de croissance de Brody, Nunavut, phocidés, pinnipèdes, Pusa hispida, phoque annelé, glace marine, dimorphisme sexuel de la taille, neige, température., Introduction Body size is strongly associated with all other life-history traits (Stearns 1983; Calder 1984). Interspecific variation in body size is thought to be due to selection pressure from environmental [...]

The forage fish communities of the Laurentian Great Lakes continue to experience changes that have altered ecosystem structure, yet little is known about how they partition resources. Seasonal, spatial, and body size variation in [delta][sup.13]C and [delta][sup.15]N was used to assess isotopic niche overlap and resource and habitat partitioning among the five common offshore Lake Ontario forage fish species (n = 2037; alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), round goby (Neogobius melanostomus), and deepwater (Myoxocephalus thompsonii) and slimy (Cottus cognatus) sculpins). Round goby had the largest isotopic niche (6.1[[per thousand].sup.2], standard ellipse area), followed by alewife (3.4[[per thousand].sup.2]), while rainbow smelt, slimy sculpin, and deepwater sculpin had the smallest and similar niche size (1.7[[per thousand].sup.2]-1.8[[per thousand].sup.2]), with only the sculpin species showing significant isotopic niche overlap (>63%). Stable isotopes in alewife, round goby, and rainbow smelt varied with location, season, and size, but did not vary in the sculpin species. Lake Ontario forage fish species have partitioned food and habitat resources, and non-native alewife and round goby have the largest isotopic niche, suggestive of a boarder ecological niche, and may contribute to their current high abundance. Si les communautes de poissons-fourrage des Grands Lacs laurentiens continuent de subir des changements qui ont modifie la structure des ecosystemes, les connaissances sur le partage des ressources dans ces communautes sont limitees. Les variations saisonnieres, spatiales et associees a la taille du corps du [delta][sup.13]C et du [delta][sup.15]N ont ete utilisees pour evaluer le chevauchement des niches isotopiques et le partage des ressources et des habitats entre cinq especes de poissons-fourrage pelagiques repandues du lac Ontario (n = 2037; le gaspareau (Alosa pseudoharengus), l'eperlan arc-en-ciel (Osmerus mordax), le gobie a taches noires (Neogobius melanostomus), le chabot de profondeur (Myoxocephalus thompsonii) et le chabot visqueux (Cottus cognatus)). Le gobie a taches noires presente la plus grande niche isotopique (6,1[[per thousand].sup.2], aire de l'ellipse standard), suivi du gaspareau (3,4[[per thousand].sup.2]), alors que l'eperlan arc-en-ciel, le chabot visqueux et le chabot de profondeur ont les plus petites niches, de tailles semblables (1,7-1,8[[per thousand].sup.2]), seuls les chabots presentant un chevauchement significatif de leurs niches isotopiques (>63 %). Les isotopes stables des gaspareaux, gobies a taches noires et eperlans arc-en-ciel varient selon le lieu, la saison et la taille, contrairement a ceux des chabots. Les especes de poissons-fourrage du lac Ontario presentent un partage des ressources alimentaires et des habitats, le gaspareau et le gobie a taches noires, des especes non indigenes, etant caracterises par les plus grandes niches isotopiques, ce qui indiquerait une niche ecologique plus large et pourrait contribuer a expliquer leur forte abondance actuelle. [Traduit par la Redaction], Introduction In the Laurentian Great Lakes (hereinafter Great Lakes), consumption by the offshore prey fish community transfers production from the lower trophic level to higher trophic levels and can influence [...]

Thermoregulation is presumed to be a widespread determinant of behaviour in fishes, but has not often been investigated as a mechanism shaping long-distance migrations. We used acoustic telemetry and animal-borne thermal loggers to test the hypothesis that seasonal migration in adult walleye (Sander vitreus) in Lake Erie is size- and (or) sex-specific and related to behavioural thermoregulation. Female walleye migrated out of the warm, shallow western basin earlier than did males and were 1.8 times more likely to be detected on acoustic receivers in the deeper and cooler eastern basin. The few fish that remained in the western basin were restricted to a smaller range of higher temperatures ([greater than or equal to]20 [degrees]C) than those that migrated to the central and eastern basins (~16-21 [degrees]C). However, temperature records from walleye in the central basin were nearly indistinguishable from those in the eastern basin, suggesting thermal preferences alone could not explain migration to the eastern basin. As such, our effort to understand the mechanisms that cause migratory behaviours has generated mixed evidence on the role of temperature and that factors like foraging opportunities may have synergistic roles in the migration. S'il est presume que la thermoregulation est un determinant repandu du comportement chez les poissons, la possibilite qu'elle puisse moduler les migrations sur de longues distances n'a pas souvent ete examinee. Nous avons utilise la telemetrie acoustique et des enregistreurs de temperature installes sur des animaux pour verifier l'hypothese selon laquelle la migration saisonniere chez les dores jaunes (Sander vitreus) adultes du lac Erie depend de la taille ou du sexe et est associee a la thermoregulation comportementale. La migration des dores femelles pour sortir du bassin ouest plus chaud et moins profond a eu lieu plus tot que celle des males, et les femelles etaient 1,8 fois plus susceptibles d'etre detectees par des recepteurs acoustiques dans le bassin est plus profond et frais. Les quelques poissons qui etaient restes dans le bassin ouest etaient limites a une petite fourchette de temperatures plus elevees ([greater than or equal to]20 [degrees]C) que celles caracterisant les poissons ayant migre vers les bassins central ou est (~16-21 [degrees]C). Cependant, les registres de temperatures des dores dans le bassin central etaient presque identiques a ceux du bassin est, ce qui indiquerait que les preferences thermiques ne peuvent a elles seules expliquer la migration vers le bassin est. Ainsi, nos efforts visant a comprendre les mecanismes qui modulent les comportements migratoires ont fait ressortir des indications mitigees sur le role de la temperature et le fait que des facteurs comme les occasions d'approvisionnement pourraient jouer des roles synergiques dans la migration. [Traduit par la Redaction], Introduction Understanding why animals migrate is fundamental to ecology, evolution, and the conservation of migratory species and their habitat (Wilcove and Wikelski 2008). Migration can be driven by a variety [...]