Search

Although submerged macrophyte (hereafter, 'macrophyte') communities are globally prevalent in low-gradient rivers, the net reach-scale effect of macrophytes on drift-feeding fish microhabitat preference is poorly understood. We used snorkeling and bioenergetics to study fish habitat selection for rainbow trout (Oncorhynchus mykiss) in the Henrys Fork, ID, USA, investigating microhabitat preference across a reach-scale gradient of macrophyte growth. Fish preferred microhabitats with deep water, low velocity, and low macrophyte coverage. Preferences for microhabitats with higher net rate of energy intake (NREI) were modulated by reach-scale macrophyte coverage, higher coverage increasing preferences for higher NREI. Macrophyte coverage was a weak positive predictor for depth and NREI, and a weak negative predictor for water velocity and median substrate. Our results suggest trade-offs between fish predation risk and bioenergetic food intake, with macrophytes modulating these trade-offs across scales by affecting reach-scale geomorphology, bioenergetics, and predation risk. As such, this study highlights the important and dynamic role that macrophytes can play in fish population dynamics in rivers, with important implications for management decisions. Key words: stream ecology, fish habitat, space use ecology, submerged macrophytes, bioenergetics, microhabitats, Introduction Clear, low-gradient lotic ecosystems throughout the world offer suitable conditions for the proliferation of submerged macrophytes, often reaching >50% areal coverage of the channel (Haslam 1978; Canfield and Hoyer [...]

Reservoirs are examples of novel ecosystems that have developed into popular sport fisheries; these systems are also becoming seasonal refuges for migratory birds, including the piscivorous American white pelican (Pelecanus erythrorhynchos). We (1) investigated the proportion of cutthroat trout (Oncorhynchus clarkii utah) and other species consumed by pelicans, (2) compared whether pelicans have an adverse effect on cutthroat trout spawning movement, and (3) determined the importance of pelican predation relative to other sources of fish mortality in Strawberry Reservoir, Utah, USA. Pelican diet samples consisted of >85% Utah sucker (Catostomus ardens), 6% Utah chub (Gila atraria), and 3% cutthroat trout. Based on bioenergetics, we estimated that pelicans consumed 384-3020 individual cutthroat trout (0.17%-1.3% of population), in contrast to 14166-27196 nongame sucker and chub. Bird-related mortality rate ranged from 1% to 6% for stocked, PIT (passive integrated transpondertagged adult cutthroat trout and from 4% to 16% for subadult cutthroat trout. Based on these results, any management action taken to control pelican predation would need to be weighed against the benefits of nongame fish removal and the protected status of pelicans. Les reservoirs constituent des exemples d'ecosystemes nouveaux qui sont devenus des ressources prisees pour la peche sportive. Ces systemes deviennent aussi des refuges saisonniers pour des oiseaux migrateurs, dont le pelican d'Amerique (Pelecanus erythrorhynchos), une espece piscivore. Nous (1) etudions les proportions de truites fardees (Oncorhynchus clarkii utah) et d'autres especes consommees par les pelicans, (2) verifions si les pelicans ont un effet negatif sur les deplacements de reproduction des truites fardees et (3) determinons l'importance de la predation par les pelicans relativement a d'autres sources de mortalite de poissons dans le reservoir Strawberry (Utah, Etats-Unis). Des echantillons du regime alimentaire des pelicans sont constitues a >85 % de surgeons de l'Utah (Catostomus ardens), 6 % de chevesnes de l'Utah (Gila atraria) et 3 % de truites fardees. Sur la base de la bioenergetique, nous estimons que les pelicans ont consomme de 384 a 3020 truites fardees (de 0,17 % a 1,3 % de la population), comparativement a de 14 166 a 27 196 surgeons et chevaines, des especes non pechees. Le taux de mortalite associe aux oiseaux va de 1 % a 6 % pour les truites fardees adultes empoissonnees dotees de transpondeurs passifs integres et de 4 % a 16 % pour les truites fardees subadultes. A la lumiere de ces resultats, toute mesure de gestion prise pour controler la predation par les pelicans devrait etre soupesee par rapport aux avantages decoulant du retrait de poissons non peches et au statut protege des pelicans. [Traduit par la Redaction], Introduction Global alterations to landscape structure and species assemblages have led to the development of 'novel ecosystems' differing in composition and function from historical conditions (Hobbs et al. 2006). In [...]

MotivationThe BioTIME database contains raw data on species identities and abundances in ecological assemblages through time. These data enable users to calculate temporal trends in biodiversity within and amongst assemblages using a broad range of metrics. BioTIME is being developed as a community-led open-source database of biodiversity time series. Our goal is to accelerate and facilitate quantitative analysis of temporal patterns of biodiversity in the Anthropocene.Main types of variables includedThe database contains 8,777,413 species abundance records, from assemblages consistently sampled for a minimum of 2 years, which need not necessarily be consecutive. In addition, the database contains metadata relating to sampling methodology and contextual information about each record.Spatial location and grainBioTIME is a global database of 547,161 unique sampling locations spanning the marine, freshwater and terrestrial realms. Grain size varies across datasets from 0.0000000158 km2 (158 cm2) to 100 km2 (1,000,000,000,000 cm2).Time period and grainBioTIME records span from 1874 to 2016. The minimal temporal grain across all datasets in BioTIME is a year.Major taxa and level of measurementBioTIME includes data from 44,440 species across the plant and animal kingdoms, ranging from plants, plankton and terrestrial invertebrates to small and large vertebrates.Software format.csv and .SQL.

Increasing water demand, water development, and ongoing climate change have driven extensive changes to the hydrology, geomorphology and biology of arid-land rivers globally, driving an increasing need to understand how annual hydrologic conditions affect the distribution and abundance of imperiled desert fish populations. We analyzed the relationship between annual hydrologic conditions and the endangered Rio Grande silvery minnow (Hybognathus amarus) in the Middle Rio Grande, New Mexico, USA, using hurdle models to predict both presence and density as a function of integrated annual hydrologic metrics. Both presence and density were positively related to spring high flow magnitude and duration and negatively related to summer drying, as indicated by an integrated flow metric. Simulations suggest hydrologic conditions near the wettest observed in the data set would be required to meet recovery goals in a single year in all reaches. We demonstrate how the models developed herein can be used to examine alternative water management strategies, including strategies that may currently be socially and logistically infeasible to implement, to identify strategies minimizing tradeoffs between conservation and other management goals. L'augmentation de la demande d'eau, l'amenagement hydraulique et les changements climatiques en cours ont cause d'importants changements a l'hydrologie, la geomorphologie et la biologie des rivieres de regions arides partout sur terre, rehaussant du coup l'importance de comprendre l'incidence des conditions hydrologiques annuelles sur la repartition et l'abondance des populations en peril de poissons du desert. Nous analysons la relation entre les conditions hydrologiques annuelles et le mene d'argent du Rio Grande (Hybognathus amarus), une espece en voie de disparition, dans le cours intermediaire du Rio Grande (Nouveau-Mexique, Etats-Unis), en utilisant des modeles d'obstacles pour predire a la fois la presence et la densite en fonction de parametres hydrologiques annuels integres. La presence et la densite sont toutes deux reliees positivement a la magnitude et a la duree des debits de crue printaniers et negativement a l'assechement estival, comme l'indique une mesure integree du debit. Des simulations donnent a penser que des conditions hydrologiques s'approchant des conditions les plus humides de l'ensemble de donnees seraient requises pour atteindre les objectifs de retablissement en une seule annee dans tous les troncons. Nous demontrons comment les modeles presentes peuvent etre utilises pour examiner differentes strategies de gestion de l'eau, y compris des strategies dont la mise en oeuvre pourrait ne pas etre possible actuellement pour des raisons sociales ou logistiques, afin de cerner des strategies qui minimisent les compromis entre la conservation et d'autres objectifs de gestion. [Traduit par la Redaction], Introduction Freshwater ecosystems are home to a disproportionate degree of global biodiversity. While freshwater habitats cover less than 1% of the Earth's surface, they contain nearly 9.5% of the planet's [...]

Flow alteration and riparian vegetation encroachment are causing habitat simplification with severe consequences for native fishes. To assess the effectiveness of enhancing simplified habitat in a large dryland river, we experimentally added invasive wood at 19 paired treatment and reference (no wood added) subreaches (50–100 m) within the main channel of the San Juan River. Using a before‐after‐control‐impact design, we sampled fishes and macroinvertebrates, and quantified habitat complexity. After wood addition, total native fish densities were 2.2× higher in treatments compared with references, whereas total nonnative fish densities exhibited no response. Macroinvertebrate densities were 6.8× higher, and habitat complexity increased in treatments. Counts of geomorphic features in treatments increased from 1 to a maximum of 11 following wood addition, while the number of features in references remained unchanged. Wood addition has potential to instigate natural riverine processes, ultimately enhancing native fish habitat by increasing macroinvertebrate densities and habitat complexity in dryland rivers. Water overallocation and increasing aridity will continue to challenge efforts to improve habitat conditions with environmental flows alone, and managers might consider integrating non‐flow alternatives like addition of abundant, invasive wood to reduce habitat simplification. [ABSTRACT FROM AUTHOR]

Stream habitat changes affecting primary consumers often indirectly impact secondary consumers such as fishes. Blooms of the benthic algae Didymosphenia geminata (Didymo) are known to affect stream macroinvertebrates, but the potential indirect trophic impacts on fish consumers are poorly understood. In streams of the Kootenai River basin, we quantified the diet, condition, and growth rate of species of trout, char, and sculpin. In 2018, macroinvertebrate taxa composition was different between a stream with Didymo and a stream without, but trout diets, energy demand, and growth rates were similar. Trout abundance was higher in the stream with Didymo, but the amount of drifting invertebrates was higher in the stream without. In 2019, we surveyed 28 streams with a gradient of coverage. Didymo abundance was correlated only with the percentage of aquatic invertebrates in trout diets and was not related to diets of char or sculpin or condition of any species. Thus, we found no evidence for a trophic link between Didymo blooms and the condition or growth of trout, char, or sculpin in mountainous headwater streams. Les modifications des habitats de cours d'eau qui ont une incidence sur les consommateurs primaires ont souvent des effets indirects sur les consommateurs secondaires comme les poissons. S'il est etabli que les proliferations de l'algue benthique Didymosphenia geminata (didymo) ont une incidence sur les macroinvertebres lotiques, leurs impacts trophiques indirects potentiels sur les poissons consommateurs ne sont pas bien compris. Nous avons quantifie le regime alimentaire, l'embonpoint et le taux de croissance de truites, d'ombles et de chabots dans des cours d'eau du bassin de la riviere Kootenai. En 2018, un cours d'eau ou l'algue didymo etait presente et un autre dont elle etait absente presentaient des compositions taxonomiques de macroinvertebres differentes, alors que les regimes alimentaires, la demande energetique et les taux de croissance des truites y etaient semblables. L'abondance de truites etait plus grande dans le cours d'eau contenant des algues didymo, mais la quantite d'invertebres a la derive etait plus grande dans le cours d'eau exempt de l'algue. En 2019, nous avons inventorie 28 cours d'eau definissant un gradient de couverture par l'algue didymo. L'abondance des algues etait seulement correlee au pourcentage d'invertebres aquatiques dans le regime alimentaire des truites et n'etait pas correlee au regime alimentaire des ombles ou des chabots, ni a l'embonpoint d'aucune espece. Ainsi, nous n'avons releve aucune preuve d'un lien entre les proliferations d'algues didymo et l'embonpoint ou la croissance des truites, ombles ou chabots dans des cours d'eau superieurs de montagne. [Traduit par la Redaction], Introduction Trophic structure determines the availability of food resources to organisms within a food web. The growth of these organisms depends not only on the amount of energy in a [...]

The ability of passive integrated transponder (PIT) tag data to improve demographic parameter estimates has led to the rapid advancement of PIT tag systems. However, ghost tags create uncertainty about detected tag status (i.e., live fish or ghost tag) when using mobile interrogation systems. We developed a method to differentiate between live fish and ghost tags using a random forest classification model with a novel data input structure based on known fate PIT tag detections in the San Juan River (New Mexico, Colorado, and Utah, USA). We used our model to classify detected tags with an overall error rate of 6.8% (1.6% ghost tags error rate and 21.8% live fish error rate). The important variables for classification were related to distance moved and response to monsoonal flood flows; however, habitat variables did not appear to influence model accuracy. Our results and approach allow the use of mobile detection data with confidence and allow for greater accuracy in movement, distribution, and habitat use studies, potentially helping identify influential management actions that would improve our ability to conserve and recover endangered fish. Les donnees de transpondeurs passifs integres (PIT) ont permis d'ameliorer les estimations de parametres demographiques, ce qui a engendre une progression rapide des systemes d'etiquettes PIT. Les etiquettes fantomes generent toutefois une incertitude quant au statut des etiquettes detectees (c.-a-d. poisson vivant ou etiquette fantome) quand des systemes d'interrogation mobiles sont utilises. Nous avons mis au point une methode pour distinguer les poissons vivants des etiquettes fantomes qui fait appel a un modele de classification par arbres decisionnels integrant une structure d'entree de donnees novatrice basee sur les detections d'etiquettes PIT de destin connu dans la riviere San Juan (au Nouveau-Mexique, au Colorado et en Utah, Etats-Unis). Nous avons utilise le modele pour classer les etiquettes detectees avec un taux d'erreurs global de 6,8% (taux d'erreurs de 1,6% pour les etiquettes fantomes et de 21,8% pour les poissons vivants). Les variables importantes pour la classification sont reliees a la distance parcourue et la reaction aux debits de crue de mousson; les variables associees a l'habitat ne semblent cependant pas influencer l'exactitude du modele. Nos resultats et notre approche permettent l'utilisation fiable de donnees de detection mobile et une plus grande exactitude dans les etudes des deplacements, de la repartition et des habitats, ce qui pourrait aider a cerner des mesures de gestion efficaces pour ameliorer la conservation et le retablissement d'especes de poissons menacees., Introduction Successful management of sport fisheries, conservation of native fish, and endangered species recovery rely on the ability to accurately assess the effectiveness of focused management actions (Parma 1998; Pine [...]

Recovery of imperiled fishes can be achieved through suppression of invasives, but outcomes may vary with environmental conditions. We studied the response of imperiled desert fishes to an invasive brown (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) suppression program in a Colorado River tributary, with natural flow and longitudinal variation in thermal characteristics. We investigated trends in fish populations related to suppression and tested hypotheses about the impacts of salmonid densities, hydrologic variation, and spatial-thermal gradients on the distribution and abundance of native fish species using zero-inflated generalized linear mixed effects models. Between 2012 and 2018, salmonids declined 89%, and native fishes increased dramatically (~480%) once trout suppression surpassed ~60%. Temperature and trout density were consistently retained in the top models predicting the abundance and distribution of native fishes. The greatest increases occurred in warmer reaches and in years with spring flooding. Surprisingly, given the evolution of native fishes in disturbance-prone systems, intense, monsoon-driven flooding limited native fish recruitment. Applied concertedly, invasive species suppression and efforts to mimic natural flow and thermal regimes may allow rapid and widespread native fish recovery. Le retablissement d'especes de poissons en peril peut se faire par la suppression d'especes envahissantes, mais les resultats peuvent dependre des conditions ambiantes. Nous avons etudie la reaction de poissons de regions desertiques en peril a un programme de suppression des truites brunes (Salmo trutta) et des truites arc-en-ciel (Oncorhynchus mykiss) envahissantes dans un affluent du fleuve Colorado, en fonction de l'ecoulement naturel et des variations longitudinales des caracteristiques thermiques. Nous avons examine les tendances au sein de populations de poissons associees a la suppression et avons teste des hypotheses concernant les effets de la densite de salmonides, des variations hydrologiques et des gradients thermiques sur la repartition et l'abondance d'especes de poissons indigenes en utilisant des modeles lineaires generalises a effets mixtes avec inflation du zero. De 2012 a 2018, les salmonides ont connu une baisse de 89% et les poissons indigenes, une augmentation marquee (~480%) une fois que la suppression des truites a depasse ~60%. La temperature et la densite des truites etaient des variables uniformement retenues dans les modeles predisant le mieux l'abondance et la repartition de poissons indigenes. Les augmentations les plus importantes se sont produites dans les tronqons plus chauds et durant des annees d'inondations printanieres. Etonnamment, vu Devolution des poissons indigenes dans les systemes frequemment perturbes, des inondations intenses associees a la mousson limitaient le recrutement de poissons indigenes. Appliques de maniere concertee, la suppression d'especes envahissantes et des efforts visant a reproduire l'ecoulement et les regimes thermiques naturels pourraient permettre le retablissement rapide et repandu d'especes de poissons indigenes., Introduction Freshwater ecosystems are heavily modified world-wide, and consequently native fishes are threatened by a variety of persistent and emerging factors, including invasive species, hydropower generation and river regulation, climate [...]

The inclusion of passive interrogation antenna (PIA) detection data has promise to increase precision of population abundance estimates ([??]). However, encounter probabilities are often higher for PIAs than for physical capture. If the difference is not accounted for, [??] may be biased. Using simulations, we estimated the magnitude of bias resulting from mixed capture and detection probabilities and evaluated potential solutions for removing the bias for closed capture models. Mixing physical capture and PIA detections ([p.sub.det]) resulted in negative biases in [??]. However, using an individual covariate to model differences removed bias and improved precision. From a case study of fish making spawning migrations across a stream-wide PIA ([p.sub.det] [less than or equal to] 0.9), the coefficient of variation (CV) of [??] declined 39%-82% when PIA data were included, and there was a dramatic reduction in time to detect a significant change in [??]. For a second case study, with modest [p.sub.det] ([less than or equal to] 0.2) using smaller PIAs, CV ([??]) declined 4%-18%. Our method is applicable for estimating abundance for any situation where data are collected with methods having different capture-detection probabilities. L'inclusion de donnees de detection par antennes d'interrogation passives (AIP) a le potentiel d'accroitre la precision des estimations d'abondance de populations ([??]). Les probabilites de rencontres sont toutefois plus elevees pour les AIP que pour la capture physique. La non prise en compte de cette difference peut se traduire par un biais des valeurs de [??]. En utilisant des simulations, nous estimons la magnitude du biais decoulant de probabilites de capture et de detection mixtes et evaluons des solutions possibles pour retirer ce biais pour des modeles de capture fermee. Le melange de captures physiques et de detections par AIP ([p.sub.det]) produit des biais negatifs de [??]. L'utilisation d'une covariable individuelle pour modeliser les differences enleve le biais et ameliore la precision. A partir d'une etude de cas de poissons effectuant des migrations de frai captes par des AIP dans tout le cours d'eau ([p.sub.det] [less than or equal to] 0,9), le coefficient de variation (CV) de N diminue de 39-82 % quand les donnees d'AIP sont incluses, et il y a une reduction marquee du temps necessaire pour detecter un changement significatif de [??]. Pour une deuxieme etude de cas caracterisee par de modestes [p.sub.det] ([less than or equal to] 0,2) et utilisant de plus petites AIP, le CV ([??]) diminue de 4-18 %. Notre methode peut etre appliquee pour estimer l'abondance pour toute situation ou les donnees sont obtenues par des methodes presentant differentes probabilites de capture-detection., Introduction Estimating abundance remains one of the most challenging and important activities in the conservation and management of animals. Ecologists and managers alike want to know 'how many are there' [...]

An editorial is presented with brief items on a variety of editorial topics including journal impact, editorial practices, and the editorial board and reviewers. Topics include the top ten most-cited papers for 2020 to 2021, changes in senior editors and performance metrics. [Extracted from the article]

Widespread hydrologic alterations have simplified in‐stream habitats in rivers globally, driving population declines and extirpations of many native fishes. Here, we examine how rapid geomorphic change in a historically degraded desert river has influenced habitat diversification and ecosystem persistence. In 2010, a large reach of the degraded and simplified lower San Rafael River (SRR), Utah, was impacted by the formation of a valley plug and began to shift from a homogenous, single‐thread channel to a complex, multi‐threaded riverscape. We combined field measurements and drone‐collected imagery to document changes in fish habitat due to the valley plug. Our results demonstrate that in 2021, the affected reach was more diverse than any other stream reach along the SRR, containing 641% more diverse habitat (e.g., pools, riffles, and backwaters) than what was measured in 2015. The plug reach also retained water for periods beyond what was expected during seasonal drying, with the total extent of inundation within the riverscape increasing by over 2800%. Since the formation of the valley plug, riparian habitat has increased by 230% and channel networks have expanded to more than 50 distinct channels throughout the zone of influence. Our results provide evidence of successful self‐restoration in a formerly highly degraded reach of desert river, and encourage new methods of desert river restoration. We aim to inform the use of large‐scale, disruptive restoration actions like intentional channel occlusions, with the goal of mitigating the impacts of simplification and increasing habitat persistence in the face of exacerbated aridity in the desert Southwest. [ABSTRACT FROM AUTHOR]

Environmental DNA (eDNA) sampling has proven to be a valuable tool for detecting species in aquatic ecosystems. Within this rapidly evolving field, a promising application is the ability to obtain quantitative estimates of relative species abundance based on eDNA concentration rather than traditionally labor-intensive methods. We investigated the relationship between eDNA concentration and Arctic char (Salvelinus alpinus) abundance in five well-studied natural lakes; additionally, we examined the effects of different temporal (e.g., season) and spatial (e.g., depth) scales on eDNA concentration. Concentrations of eDNA were linearly correlated with char population estimates ([R.sup.2.sub.adj] = 0.78) and exponentially correlated with char densities ([R.sup.2.sub.adj] = 0.96 by area; 0.82 by volume). Across lakes, eDNA concentrations were greater and more homogeneous in the water column during mixis; however, when stratified, eDNA concentrations were greater in the hypolimnion. Overall, our findings demonstrate that eDNA techniques can produce effective estimates of relative fish abundance in natural lakes. These findings can guide future studies to improve and expand eDNA methods while informing research and management using rapid and minimally invasive sampling. Resume : L'echantillonnage d'ADN environnemental (ADNe) est un outil qui s'est avere utile pour detecter la presence d'especes dans les ecosystemes aquatiques. Une des applications prometteuses dans ce domaine en evolution rapide consiste en la capacite d'obtenir des estimations quantitatives de l'abondance relative d'especes a la lumiere des concentrations d'ADNe plutot que par des methodes traditionnelles qui demandent beaucoup d'efforts. Nous avons examine la relation entre les concentrations d'ADNe et l'abondance d'ombles arctiques (Salvelinus alpinus) dans cinq lacs naturels bien etudies, ainsi que les effets de differentes echelles temporelles (p. ex. saison) et spatiales (p. ex. profondeur) sur les concentrations d'ADNe. Ces concentrations presentent une correlation lineaire avec les estimations des populations d'ombles ([R.sup.2.sub.adj] = 0,78) et une correlation exponentielle avec les densites d'ombles ([R.sup.2.sub.adj] = 0,96 en superficie, 0,82 en volume). Pour les cinq lacs, les concentrations d'ADNe etaient plus grandes et plus homogenes dans la colonne d'eau durant le brassage; cependant, quand elles etaient stratifiees, les concentrations d'ADNe etaient plus elevees dans l'hypolimnion. Globalement, nous resultats demontrent que les methodes reposant sur l'ADNe peuvent produire des estimations valables de l'abondance relative des poissons dans les lacs naturels. Ces constatations peuvent orienter les etudes futures visant a ameliorer et elargir les methodes reposant sur l'ADNe et fournir de l'information utile pour la recherche et la gestion faisant appel a un echantillonnage rapide et d'impact minimum. [Traduit par la Redaction], Introduction Reliable estimates of fish abundance are necessary for making effective conservation and management decisions (Dudgeon et al. 2005). However, obtaining these estimates can be expensive and time consuming and [...]

Temporal symmetry models (TSM) represent advances in the analytical application of mark-recapture data to population status assessments. For a population of char, we employed 10 years of active and passive mark-recapture data to quantify population growth rates using different data sources and analytical approaches. Estimates of adult population growth rate were 1.01 (95% confidence interval = 0.84-1.20) using a temporal symmetry model ([[lambda].sub.TSM]), 0.96 (0.68-1.34) based on logistic regressions of annual snorkel data ([[lambda].sub.A]), and 0.92 (0.77-1.11) from redd counts ([[lambda].sub.R]). Top-performing TSMs included an increasing time trend in recruitment (f) and changes in capture probability (p). There was only a 1% chance the population decreased [greater than or equal to] 50%, and a 10% chance it decreased [greater than or equal to] 30% ([[lambda].sub.MCMC]; based on Bayesian Markov chain Monte Carlo procedure). Size structure was stable; however, the adult population was dominated by small adults, and over the study period there was a decline in the contribution of large adults to total biomass. Juvenile condition decreased with increasing adult densities. Utilization of these different information sources provided a robust weight-of-evidence approach to identifying population status and potential mechanisms driving changes in population growth rates. Les modeles de symetrie temporelle (TSM) representent des avancees dans l'application analytique des donnees de marquage-recapture aux evaluations de situation. Pour une population d'ombles, nous avons utilise 10 annees de donnees de marquage-recapture actives et passives pour quantifier les taux de croissance de la population en utilisant differentes sources de donnees et approches analytiques. Les estimations du taux de croissance de la population d'adultes etaient de 1,01 (intervalle de confiance de 95 % = 0,84-1,20) en utilisant un modele de symetrie temporelle ([[lambda].sub.TSM]), de 0,96 (0,68- 1,34) a la lumiere de regressions logarithmiques de donnees annuelles de releves au tuba ([[lambda].sub.A]) et de 0,92 (0,77-1,11) sur la base de denombrements de nids de frai ([[lambda].sub.R]). Les TSM qui donnaient les meilleurs resultats integraient une tendance d'augmentation du recrutement (f) dans le temps et des variations de la probabilite de prise (p). La probabilite que la population diminue de [greater than or equal to] 50 % n'etait que de 1 % et celle que la population diminue de [greater than or equal to] 30 % ([[lambda].sub.MCMC]; base sur la procedure bayesienne de Monte Carlo de la chaine de Markov), de 10 %. Si la structure selon la taille etait stable, la population d'adultes etait dominee par de petits adultes et, durant la periode de l'etude, il y a eu une baisse de la contribution des grands adultes a la biomasse totale. L'embonpoint des juveniles diminuait quand la densite d'adultes augmentait. L'utilisation de ces differentes sources d'information offre une approche robuste reposant sur le poids des donnees probantes pour determiner la situation de populations et les mecanismes qui pourraient etre a l'origine de variations des taux de croissance de populations. [Traduit par la Redaction], Introduction Population growth rates, or the rate of change in a population, is an important viability metric describing the cumulative effects of survival and mortality over time. Accordingly, quantifying population [...]

In reservoirs, seasonal drawdown can alter the physical environment and may influence predatory fish performance. We investigated the performance of lake trout (Salvelinus namaycush) in a western reservoir by coupling field measurements with visual foraging and bioenergetic models at four distinct states (early summer, mid-summer, late summer, and fall). The models suggested that lake trout prey, juvenile kokanee (Oncorhynchus nerka), are limited seasonally by suitable temperature and dissolved oxygen. Accordingly, prey densities were greatest in late summer when reservoir volume was lowest and fish were concentrated by stratification. Prey encounter rates (up to 68 fish-day-1) and predator consumption are also predicted to be greatest during late summer. However, our models suggested that turbidity negatively correlates with prey detection and consumption across reservoir states. Under the most turbid conditions, lake trout did not meet physiological demands; however, during less turbid periods, predator consumption reached maximum bioenergetic efficiency. Overall, our findings demonstrate that rapid reservoir fluctuations and associated abiotic conditions can influence predator-prey interactions, and our models describe the potential impacts of water level fluctuation on valuable sport fishes. Dans les reservoirs, l'abaissement saisonnier du niveau d'eau peut modifier le milieu physique et influencer la performance des poissons predateurs. Nous avons etudie la performance des truites grises (Salvelinus namaycush) dans un reservoir de l'Ouest en combinant des mesures de terrain a des modeles d'approvisionnement et de bioenergetique pour quatre etats distincts du reservoir (debut de l'ete, milieu de l'ete, fin de l'ete et automne). Les modeles donnent a penser que l'abondance saisonniere des proies des truites, les saumons rouges (Oncorhynchus nerka) juveniles, est limitee par la temperature et l'oxygene dissous. Ainsi, les densites de proies etaient les plus grandes a la fin de l'ete, quand le volume du reservoir etait a son plus faible et les poissons etaient concentres par la stratification. Il est egalement predit que la frequence des rencontres de proie (jusqu'il 68 poissons-jour-1) et la consommation des predateurs sont plus elevees a la fin de l'ete. Cependant, nos modeles suggerent une correlation negative entre la turbidite, d'une part, et la detection et la consommation de proies pour tous les etats du reservoir. Dans les conditions les plus turbides, les truites grises ne repondaient pas a leur demande physiologique; cependant, durant les periodes de plus faible turbidite, la consommation des predateurs atteignait l'efficacite bioenergetique maximum. Globalement, nos resultats demontrent que des fluctuations rapides des reservoirs et les conditions abiotiques associees peuvent influencer les interactions predateurs-proies et nos modeles decrivent les impacts potentiels des fluctuations du niveau de l'eau sur des poissons d'interet pour la peche sportive. [Traduit par la Redaction]., Introduction Reservoir water quality and availability can change temporally and spatially as a result of climate-driven variation in physical, chemical, and biological conditions (Williamson et al. 2009; Carpenter et al. [...]

Successful spawning is imperative for the persistence of salmonid populations, but relatively little research has been conducted to evaluate factors affecting early life-stage survival for bull trout (Salvelinus confluentus), a threatened char. We conducted a field experiment to assess the relationship between site-specific environmental factors and bull trout embryo survival and fry emergence timing. Survival from egg to hatch was negatively related to percent fine sediment ( Si le succes du frai est un imperatif pour la persistance des populations de salmonides, assez peu de travaux se sont penches sur revaluation des facteurs ayant une incidence sur la survie des premiers stades du cycle de vie de l'omble a tete plate (Salvelinus confluentus), une espece menacee. Nous avons mene une experience de terrain visant a evaluer le lien entre les facteurs ambiants propres au site, d'une part, et la survie des embryons et le moment de l'emergence des alevins, d'autre part. La survie des embryons jusqu'a l'eclosion presentait une relation negative avec le pourcentage de sediments fins (, Introduction Within the overall salmonid life cycle, a large but variable proportion of mortality occurs between the period of egg deposition and fry emergence. Because of the importance of this [...]