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Understanding the space use of fishes in early life stages provides information that can contribute to effective fisheries management; however, it can be difficult to track fish in shallow, densely vegetated areas. Using acoustic telemetry, 60 subadult yellow perch (Perca flavescens) were tagged and monitored in a vegetated area of the Detroit River (May-November 2018). Variable detection range from submerged aquatic vegetation (SAV) was incorporated in estimates by applying a spatiotemporal correction to aid with interpretation of seasonal changes in activity space. Although subadult yellow perch were commonly detected in the array, demonstrating the importance of SAV habitat (mean detection residency index: 0.85), 60% of individuals were not detected following August, the period with highest activity space estimates, likely due to seasonal movements and predation. Individuals were more commonly detected during the daylight hours compared to night, but activity peaked at crepuscular periods. This study provided spatial information about the often-overlooked early life history of yellow perch, increasing the ecological information available for a species of management and conservation interest in the Great Lakes. Si la comprehension de l'utilisation de l'espace par les poissons durant les premieres etapes du cycle de vie fournit des renseignements utiles pour une gestion efficace des peches, il peut etre difficile de suivre les poissons dans des zones peu profondes et a vegetation dense. La telemetrie acoustique a ete utilisee pour suivre 60 perchaudes (Perca flavescens) subadultes etiquetees dans un secteur vegetalise de la riviere Detroit (de mai a novembre 2018). La portee de detection variable decoulant de la vegetation aquatique immergee (VAI) a ete incorporee aux estimations en appliquant une correction spatiotemporelle facilitant l'interpretation des variations saisonnieres de l'espace d'activite. Bien que des perchaudes subadultes aient souvent ete detectees dans la grille, demontrant l'importance des habitats de VAI (indice moyen de residence detectee : 0,85), 60 % des individus n'ont pas ete detectes apres le mois d'aout, soit la periode pour laquelle les superficies estimees des espaces d'activite sont les plus elevees, probablement en raison de deplacements saisonniers et de la predation. Si des individus etaient plus souvent detectes durant les heures de clarte que pendant la nuit, l'activite atteignait un maximum durant les periodes crepusculaires. L'etude fournit de l'information spatiale sur le debut de la vie des perchaudes, une periode souvent negligee, accroissant ainsi l'information ecologique disponible pour une espece dont la gestion et la conservation sont d'interet dans les Grands Lacs. [Traduit par la Redaction], Introduction Examining the movement and distribution of fishes can provide insight into their fundamental ecology including habitat use and other interactions within their environment (Brownscombe et al. 2019; Selby et [...]

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 [...]

Conservation decisions surrounding which fish habitats managers choose to protect and restore are informed by fish habitat models. As acoustic telemetry has allowed for improvements in our ability to directly measure fish positions year‐round, so too have there been opportunities to refine and apply fish habitat models. In an area with considerable anthropogenic disturbance, Hamilton Harbour in the Laurentian Great Lakes, we used telemetry‐based fish habitat models to identify key habitat variables, compare habitat associations among seasons, and spatially identify the presence distribution of six fish species. Using environmental data and telemetry‐based presence–absence from 2016 to 2022, random forest models were developed for each species across seasons. Habitat variables with the highest relative importance across species included fetch, water depth, and percentage cover of submerged aquatic vegetation. The presence probability of each species was spatially predicted for each season within Hamilton Harbour. Generally, species showed a spatial range expansion with greater presence probability in the fall and winter to include parts of the harbor further offshore, and a range contraction in the spring and summer toward the nearshore, sheltered areas, with summer having the most limited habitat availability. Greater habitat suitability was predicted in western Hamilton Harbour for the majority of species, whereas the east end was less suitable and may benefit from habitat restoration. These types of fish habitat models are highly flexible and can be used with a variety of data, not just telemetry, and should be considered as an additional tool for fish habitat and fisheries managers alike. [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]

Invasive species are a key threat to biodiversity in freshwater ecosystems; and, as such, their management can be an important part of ecosystem restoration and conservation. In Hamilton Harbour, an impaired Lake Ontario embayment, invasive species are an important threat. In the early 2000s, an increase in invasive goldfish (Carassius auratus) was identified during monitoring surveys. This population of goldfish was studied via acoustic telemetry to gain knowledge about its biology to support management control options. Hamilton Harbour goldfish exhibited seasonal patterns in site and depth use, and clear preferences for over-wintering and spawning areas. Goldfish were largely resident to Hamilton Harbour with the exception of one individual. To predict when goldfish would move into spawning areas, we examined goldfish presence, abundance, and temperature at a fish-barrier connected to the harbour and developed models to predict goldfish presence based on Cumulative Growing Degree Days (CGDD) and Day of Year (DOY). Goldfish were captured in large numbers (>100 day−1) at the fishway when CGDD > 25.0 and DOY > 100; therefore, we predicted that our tagged fish would move to spawning areas when these thresholds were reached. Both models accurately predicted when tagged fish moved to spawning areas which largely occurred when water temperatures were lower (≥ 9.7 °C) than thresholds previously identified in the literature (i.e., 15.0 °C − 22.0 °C). This suggested that pre-spawn/staging behaviour was detected using telemetry driven by factors including water temperature. Results from this work will inform control strategies for goldfish, including active removal during aggregation prior to spawning. [ABSTRACT FROM AUTHOR]