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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 [...]

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 [...]

Animal movements are influenced by the environment they inhabit and the need to maximise fitness and minimise cost. As such, seasonal thermal cycles in temperate lakes play an important role in the selection of habitat by species. Lake trout Salvelinus namaycush) is a native top predator in the Laurentian Great Lakes and currently under rehabilitation in Lake Ontario. This cold, deep-water species is known to migrate to shallower depths in the autumn to spawn, but their spatial and seasonal distribution have not been examined in detail. We quantified the residency and home ranges of 24 lake trout in eastern Lake Ontario across a full year (1 May 2017 to 30 April 2018) using acoustic telemetry to assess the influence of seasonal thermal cycles. Specifically, we used three thermal logging stations in the eastern basin, 164 acoustic receivers, and a total of over 1,000,000 detections to describe seasonal distribution. We also documented occurrences of long-distance movements (via 130 acoustic receivers located in the western basin of Lake Ontario), and thus the potential spatial overlap of populations from the eastern and western basins. During stratification (1 July-1 November), lake trout (n = 24) showed a horizontally restricted distribution in regions of deeper water in eastern Lake Ontario. A variable and broad distribution was observed around the shallower Kingston Basin shoals during isothermal (1 January-30 April), spring warming (1 May-30 June; spring mix), and autumn cooling (2 November-31 December) periods. Home range sizes ranged from 0.1 to 3,966 km2 among all thermal cycles, with the largest observed during cooling autumn mix conditions driven by four individuals. Large variation in home range area was observed among individuals, and, thus, means were not statistically different between seasons. Three individuals occupied shallower shoals even during stratified conditions, and another individual crossed the entire lake from the east to the west end of Lake Ontario, travelling over 200 linear km in 17 days. Our results confirm that thermal regimes and spawning needs affect the spatial use of lake trout in Lake Ontario, but demonstrate that there are broad distributions during isothermal conditions, highly individualistic spatial utilisation, and inter-individual variation in spatial distribution and exploratory behaviour. All of these behaviours are consistent with other top predator species. Defining the spatial utilisation and distribution of individuals are important steps toward a better understanding of reintroduced species ecology in freshwater ecosystems. The variation of individual lake trout distribution across seasons implies that individuals may have different influences on the overall ecosystem function and potentially different responses to increasing water temperatures. These results suggest that an adaptive management approach is required when rehabilitating populations of this native fish where populating multiple habitats in an ecosystem is an objective in the face of a changing environment. [ABSTRACT FROM AUTHOR]

Understanding predator–prey interactions and food web dynamics is important for ecosystem‐based management in aquatic environments, as they experience increasing rates of human‐induced changes, such as the addition and removal of fishes. To quantify the post‐stocking survival and predation of a prey fish in Lake Ontario, 48 bloater Coregonus hoyi were tagged with acoustic telemetry predation tags and were tracked on an array of 105 acoustic receivers from November 2018 to June 2019. Putative predators of tagged bloater were identified by comparing movement patterns of six species of salmonids (i.e., predators) in Lake Ontario with the post‐predated movements of bloater (i.e., prey) using a random forests algorithm, a type of supervised machine learning. A total of 25 bloater (53% of all detected) were consumed by predators on average (± S.D.) 3.1 ± 2.1 days after release. Post‐predation detections of predators occurred for an average (± S.D.) of 78.9 ± 76.9 days, providing sufficient detection data to classify movement patterns. Tagged lake trout Salvelinus namaycush provided the most reliable classification from behavioural predictor variables (89% success rate) and was identified as the main consumer of bloater (consumed 50%). Movement networks between predicted and tagged lake trout were significantly correlated over a 6 month period, supporting the classification of lake trout as a common bloater predator. This study demonstrated the ability of supervised learning techniques to provide greater insight into the fate of stocked fishes and predator–prey dynamics, and this technique is widely applicable to inform future stocking and other management efforts. [ABSTRACT FROM AUTHOR]