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The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature gradients, and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of westslope cutthroat trout (Oncorhynchus clarkii lewisi) at 5,10,15, 20, and 22[degrees]C and compared temperature preference ([T.sub.pref]) of the species with non-native brook trout (Salvelinusfontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). Intermittent-flow respirometry experiments demonstrated that metabolic performance of westslope cutthroat trout was optimal at ~15[degrees]C and decreased substantially beyond this temperature, until lethal temperatures at ~25[degrees]C. Adjusted [T.sub.pref] across species were comparatively high, ranging from 17.8 to 19.9[degrees]C, with the highest [T.sub.pref] observed for westslope cutthroat trout. Results suggest that although westslope cutthroat trout is considered a cold-water species, they do not prefer or perform as well in cold water ([less than or equal to]10[degrees]C) and thus can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species-specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for westslope cutthroat trout. La temperature ambiante de l'eau exerce une forte influence sur la physiologie et le comportement des poissons. Des caracteres physiologiques associes au metabolisme, comme la capacite metabolique aerobie (AS), peuvent etre mesures le long de gradients de temperature, et la courbe de performance qui en resulte reflete la niche thermique que les poissons peuvent occuper. Nous avons mesure l'AS de la truite fardee versant de l'Ouest (Oncorhynchus clarkii lewisi) a 5,10,15, 20 et 22[degrees]C et compare la temperature de predilection ([T.sub.pref]) de cette espece a celles d'ombles de fontaine (Salvelinusfontinalis), de truites brunes (Salmo trutta) et de truites arc-en-ciel (Oncorhynchus mykiss), des especes non indigenes. Des experiences de respirometrie a debit intermittent ont demontre que la performance metabolique des truites fardees versant de l'Ouest est optimale a ~15[degrees]C et diminue considerablement au-dessus de cette temperature, jusqu'a des temperatures letales a ~25[degrees]C. Les [T.sub.pref] ajustees pour les differentes especes sont relativement elevees, allant de 17,8 a 19,9[degrees]C, la truite fardee versant de l'Ouest ayant la [T.sub.pref] observee la plus elevee. Les resultats portent a croire que, bien que la truite fardee versant de l'Ouest soit consideree comme etant une espece d'eau douce, elle ne prefere pas l'eau froide ([less than or equal to]10[degrees]C) ni ne performe particulierement bien dans ces conditions, et elle peut donc occuper des niches thermiques plus chaudes que ce que l'on croyait auparavant. La courbe de performance metabolique (AS) peut etre utilisee pour la determination de criteres thermiques propres a l'espece pour delimiter les habitats thermiques importants et orienter les efforts de conservation et de retablissement visant la truite fardee versant de l'Ouest. [Traduit par la Redaction], Introduction The influence of temperature on the metabolic rates of coldwater fishes has been widely studied (Imholt et al. 2011; Beauregard et al. 2013; Oligny-Hebert et al. 2015), and variation [...]

Objective: Documenting the movement of Channel Catfish Ictalurus punctatus through telemetry, where a transmitter tag is surgically implanted in the fish, can provide valuable insight into the species' spatial ecology and habitat use. However, since fish in the order Siluriformes can expel foreign objects such as tags from their body cavity, the utility of telemetry technology may be limited for Channel Catfish. This study aimed to determine (1) how quickly Channel Catfish reject tags that were surgically implanted into the body cavity, (2) if surgical implantation of transmitter tags causes mortality, and (3) what surgical method is best to minimize tag rejection and/or mortality. Methods: Three surgical trials were conducted on Channel Catfish (n = 24) using two tag implantation methods: a nontethered method, in which the tag was freely implanted into the body cavity, and a tethered method, where the tag was attached to the pectoral girdle. Fish were observed in the lab for 30 days for trials 1 and 2 and 225 days for trial 3 following tag implantation. Result: No complete tag rejections occurred during any of the three experimental trials. However, all five tethered fish experienced mortality during trial 3 (58-221 days postsurgery). Necropsies indicated that the tethered tagging method led to septicaemia infections and internal lacerations from the tether, which were not observed in the nontethered fish. Tags in the nontethered fish were in the process of being absorbed into the intestinal tract, which over time might have led to tag rejection. Conclusion: While rejection is possibly the end point of the nontethered tagging method, our results suggest it is nevertheless the better tagging method for Channel Catfish given higher survival. [ABSTRACT FROM AUTHOR]

Understanding how metabolic costs change in relation to increasing temperature under future climate changes is important to predict how ectotherms will be affected across the globe. In fish, whole body respiration is traditionally used to estimate aerobic performance via an organism's minimum and maximum oxygen consumption rates. However, mitochondria play a crucial role in the aerobic cascade and may be a useful surrogate of aerobic performance. To test whether whole body oxygen consumption and mitochondrial capacity are correlated, we estimated whole body metabolic and mitochondrial respiration rates (using permeabilized red muscle fibres) in brook trout (Salvelinus fontinalis (Mitchill, 1814)) at 10, 15, and 20 °C. Standard metabolic rate increased with acclimation temperature, while maximum rates were less sensitive. All mitochondrial respiration rates increased with acclimation temperature, suggesting that red muscle mitochondrial preparations may correlate to the minimal metabolic demands in this species. When expressed as relative rates of electron flow, the red muscle fibres showed no effect of temperature on mitochondrial coupling efficiency. However, there was a pattern of declining capacity to augment respiration via complex II with increasing temperature with a concomitant increase in the capacity of the phosphorylating system relative to maximal rates of mitochondrial electron flow. [ABSTRACT FROM AUTHOR]

Global warming is changing the thermal habitat of cold-water freshwater fishes, which can lead to decreased fitness and survival and cause shifts in species distributions. The Alberta population of westslope cutthroat trout (Oncorhynchus clarkii lewisi) is listed as 'Threatened' under the Canadian Species at Risk Act. The major threats to the species are the alteration in habitat and water flow, competition and hybridization with non-native trout species and climate change. Here, we conducted (i) intermittent-flow respirometry experiments with adult native westslope cutthroat trout and non-native rainbow trout (Oncorhynchus mykiss) and (ii) critical thermal maximum experiments (CTmax) with adult westslope cutthroat trout to obtain valuable input data for species distribution models. For both species, standard metabolic rate (SMR) was lower at 10°C compared to 15°C and westslope cutthroat trout had higher SMR than rainbow trout. Although there were inter-specific differences in SMR, forced aerobic scope (using a standardized chase protocol) was different at 10°C, but no significant differences were observed at 15°C because of relative smaller differences in maximum metabolic rate between the species. CTmax of westslope cutthroat trout acclimated to 10°C was 27.0 ± 0.8°C and agitation temperature was 25.2 ± 1.0°C. The results from this study will inform and parametrize cumulative effects assessments and bioenergetics habitat modelling for the recovery planning of the species. [ABSTRACT FROM AUTHOR]

The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature gradients, and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of westslope cutthroat trout (Oncorhynchus clarkii lewisi) at 5, 10, 15, 20, and 22 °C and compared temperature preference (Tpref) of the species with non-native brook trout (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). Intermittent-flow respirometry experiments demonstrated that metabolic performance of westslope cutthroat trout was optimal at ∼15 °C and decreased substantially beyond this temperature, until lethal temperatures at ∼25 °C. Adjusted Tpref across species were comparatively high, ranging from 17.8 to 19.9 °C, with the highest Tpref observed for westslope cutthroat trout. Results suggest that although westslope cutthroat trout is considered a cold-water species, they do not prefer or perform as well in cold water (≤10 °C) and thus can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species‐specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for westslope cutthroat trout. [ABSTRACT FROM AUTHOR]

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Fisheries and Oceans Canada's Species at Risk Program provides protection of the habitat necessary for the survival or recovery of listed freshwater fishes and mussels. It is well documented that the riparian zone is essential for the maintenance of freshwater aquatic habitats, fishes, and mussels. Despite this extensive body of literature, riparian features are not consistently included as Critical Habitat for listed freshwater fishes and mussels. An evidence based approach was required to guide the identification of features in the riparian zone as Critical Habitat. Riparian Critical Habitat are riparian features that: maintain the quality of aquatic features identified as Critical Habitat, and are directly used by fishes and mussels. We performed a literature review to determine the relevant riparian features, and the processes by which they affect aquatic features and water quality attributes. From these literature reviews we identified seven main processes by which riparian features affect aquatic features and water quality attributes: erosion, filtration, infiltration, isolation, meandering, shading, and subsidization. In addition, we identified riparian features that may directly support freshwater fishes and mussels' functions depending on their life history. Meta-analyses, reviews, and primary research articles were assessed to provide some guidance on the extent of riparian habitat required to support these seven processes. We outlined the current state of the literature regarding the extent of habitat required, and denoted where more empirical evidence is required. The dependencies of each process on attributes of the floodplain and other important considerations were summarised and can be consulted to determine what riparian features should be protected as Critical Habitat for a listed species. We have included additional resources to aid in the application of this guidance when defining the geographical area to be protected. Finally, five case-studies were used to provide an example of how practitioners may apply the guidance provided here to determine riparian Critical Habitat for a listed species. [ABSTRACT FROM AUTHOR]

From a conservation perspective, it is important to identify when sub-lethal temperatures begin to adversely impact an organism. However, it is unclear whether, during acute exposures, sub-lethal cellular thresholds occur at similar temperatures to other physiological or behavioural changes, or at temperatures associated with common physiological endpoints measured in fishes to estimate thermal tolerance. To test this, we estimated temperature preference (15.1±1.1°C) using a shuttle box, agitation temperature (22.0±1.4°C) as the point where a fish exhibits a behavioural avoidance response and the CTmax (28.2±0.4°C) as the upper thermal limit for 1 yr old brook trout (Salvelinus fontinalis) acclimated to 10°C. We then acutely exposed a different subset of fish to the mean temperatures associated with the pre-determined physiological endpoints and sampled tissues when they reached the target temperature or after 60 min of recovery at 10°C for transcriptomic analysis. We used qPCR to estimate mRNA transcript levels of genes associated with heat shock proteins, oxidative stress, apoptosis, and inducible transcription factors. A major shift in the transcriptome response occurred once the agitation temperature was reached, which may identify a possible link between the cellular stress response and the behavioural avoidance response., (© 2025. Published by The Company of Biologists.)

Global warming is changing the thermal habitat of cold-water freshwater fishes, which can lead to decreased fitness and survival and cause shifts in species distributions. The Alberta population of westslope cutthroat trout ( Oncorhynchus clarkii lewisi ) is listed as 'Threatened' under the Canadian Species at Risk Act . The major threats to the species are the alteration in habitat and water flow, competition and hybridization with non-native trout species and climate change. Here, we conducted (i) intermittent-flow respirometry experiments with adult native westslope cutthroat trout and non-native rainbow trout ( Oncorhynchus mykiss ) and (ii) critical thermal maximum experiments ( CT max ) with adult westslope cutthroat trout to obtain valuable input data for species distribution models. For both species, standard metabolic rate (SMR) was lower at 10°C compared to 15°C and westslope cutthroat trout had higher SMR than rainbow trout. Although there were inter-specific differences in SMR, forced aerobic scope (using a standardized chase protocol) was different at 10°C, but no significant differences were observed at 15°C because of relative smaller differences in maximum metabolic rate between the species. CT max of westslope cutthroat trout acclimated to 10°C was 27.0 ± 0.8°C and agitation temperature was 25.2 ± 1.0°C. The results from this study will inform and parametrize cumulative effects assessments and bioenergetics habitat modelling for the recovery planning of the species., (© The Author(s) 2022. Published by Oxford University Press and the Society for Experimental Biology.)