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Before-after, control-impact (BACI) experimental designs are commonly used in large-scale environmental experiments, but these designs can be confounded by location and time interactions. Staircase designs, where replicate treatments are staggered temporally, have been suggested as an alternative to BACI designs. We performed a simulation study based on data from an ongoing watershed-scale restoration experiment within three streams to test the effectiveness of adding large wood to increase habitat complexity and abundance and productivity of juvenile steelhead (Oncorhynchus mykiss). We compared the power of two asymmetric BACI (aBACI) designs with two staircase designs for detecting changes in the density of steelhead (fish*m-2). A staircase design where treatments were temporally staggered in one treatment section in each stream had the highest power and best precision, especially when the innate spatial and temporal variances of steelhead density were large. A traditional BACI performed the worst, and a variation on another BACI and staircase design had intermediate performance. Multistream staircase designs are also more logistically and economically feasible and can maximize learning by replicating experiments across different stream types. Des schemas experimentaux avant-apres, temoin-impact (AATI) sont couramment employes dans des experiences environnementales a grande echelle, meme si une confusion decoulant des interactions du lieu et du moment peut y etre associee. Il a ete propose que les schemas en escalier, dans lesquels des traitements repetes sont decales dans le temps, pourraient constituer une solution de rechange aux schemas AATI. Nous avons effectue une etude de simulation reposant sur des donnees issues d'une experience de restauration en cours a l'echelle du bassin versant dans trois cours d'eau, afin de verifier l'efficacite de l'ajout de grands debris ligneux pour accroitre la complexite des habitats et l'abondance et la productivite des truites arc-enciel anadromes (Oncorhynchus mykiss) juveniles. Nous avons compare l'efficacite de deux schemas AATI asymetriques (AATIa) et de deux schemas en escalier pour ce qui est de detecter les variations de la densite des truites arc-en-ciel anadromes (poissons*[m.sup.-2]). Un schema en escalier dans lequel les traitements sont decales dans le temps dans un troncon traite de chaque cours d'eau produit la plus grande efficacite et la plus grande precision, particulierement quand les variances spatiales et temporelles innees de la densite des truites sont grandes. Un schema AATI traditionnel donne les pires resultats et une variation sur un autre schema AATI et en escalier produit des resultats de qualite intermediaire. Les schemas en escalier a cours d'eau multiples presentent egalement une plus grande faisabilite logistique et economique et peuvent maximiser les apprentissages en permettant de reproduire des experiences dans differents types de cours d'eau. [Traduit par la Redaction], Introduction Ecosystem experiments using impacts (e.g., perturbations such as logging, addition of nutrients) have led to a greater understanding of the influence of management actions on ecosystem processes and biological [...]

Freshwater habitat restoration is a major conservation objective, motivating efforts to restore habitat complexity and quality for fishes. Restoration based on the engineering activities of beavers (Castor canadensis) increases fish habitat complexity, but how this affects fish habitat use and movement behaviours is not well known. We used a network of passive integrated transponder antennas to quantify small-scale movement and microhabitat use of 175 individual juvenile steelhead (Oncorhynchus mykiss) in a stream channel with a complex bathymetric profile resulting from a beaver impoundment and in a simplified channel devoid of beaver activity. Our results show that juvenile steelhead exploit microhabitat heterogeneity by employing a range of behaviours that maximizes available habitat via spatial and temporal partitioning among individuals. These results suggest spatial resource partitioning as a potential mechanism for the previously established positive correlations among steelhead density, survival, and production with beaver-based restoration within the study watershed. More broadly, our findings provide insight as to how populations can exploit habitat complexity through spatial partitioning that can be informative for planning restoration and management actions. La restauration des habitats d'eau douce constitue un important objectif de conservation a l'origine d'efforts pour retablir la complexite et la qualite d'habitats pour les poissons. Si la restauration reposant sur les activites de genie civil des castors (Castor canadensis) accroit la complexite des habitats de poissons, son incidence sur l'utilisation de l'habitat et les comportements de deplacement des poissons demeure meconnue. Nous avons utilise un reseau d'antennes a radio-etiquettes passives integrees pour quantifier les deplacements a petite echelle et l'utilisation de microhabitats par 175 truites arc-en-ciel (Oncorhynchus mykiss) juveniles dans le chenal d'un cours d'eau au profil bathymetrique complexe cause par une digue de castor, et dans un chenal simplifie exempt d'activite de castors. Nos resultats montrent que les truites arc-en-ciel juveniles exploitent l'heterogeneite des microhabitats en ayant recours a un eventail de comportements qui maximise l'habitat disponible grace au partage spatial et temporel de l'habitat entre individus. Ces resultats suggerent que le partage spatial des ressources est un mecanisme qui pourrait expliquer les correlations positives deja etablies entre la densite, la survie et la production de truites arc-en-ciel et la restauration reposant sur les castors dans le bassin versant etudie. Plus largement, nos constatations fournissent de l'information sur la maniere dont les populations peuvent exploiter la complexite de l'habitat grace au partage spatial de ce dernier, qui peut eclairer la planification d'interventions de restauration et d'amenagement., Introduction Habitat degradation is one of the principal threats to freshwater populations worldwide (Dudgeon et al. 2005), with over a third of the rivers in the United States designated as [...]

Substantial research effort has been devoted to understanding stream-dwelling salmonids' use of summer rearing and growth habitat, with a subset of studies focusing on foraging position selection and the energetic trade-offs of differential habitat use. To date, however, cost-benefit analyses for most foraging model studies have focused on small sampling areas such as individual habitat units. To address this knowledge gap, we applied a mechanistic foraging model to 22 stream reaches (100-400 m) from two watersheds within the Columbia River Basin. We found a strong, positive correlation ([R.sup.2] = 0.61, p < 0.001) between predicted carrying capacities and observed fish densities. Predicted proportion of suitable habitat was weakly correlated with observed fish density ([R.sup.2] = 0.18, p = 0.051), but the mean net rate of energy intake prediction in sampling reaches was not a significant predictor of observed fish biomass. Our results suggest spatial configuration of habitat, in addition to quantity and quality, is an important determinant of habitat use. Further, carrying capacity predicted by the model shows promise as a habitat metric. We also evaluated the feasibility of applying this data- intensive modeling approach in a large-scale monitoring program to examine habitat quality and quantity. Though the approach can be computationally expensive, we feel the model's ability to integrate physical habitat metrics (e.g., depth, velocity) with important biological considerations like food availability and temperature is a benefit that far outweighs associated costs. We feel this modeling approach has great potential as a tool to help understand habitat use in drift-feeding fishes. D'importants efforts de recherche ont ete voues a la comprehension de l'utilisation d'habitats estivaux d'alevinage et de croissance par les salmonides de cours d'eau, dont un sous-ensemble d'etudes s'etant axe sur la selection de la position d'approvisionnement et les compromis energetiques associes a l'utilisation differentielle d'habitats. Les analyses coutsavantages realisees a ce jour pour la plupart des etudes de modeles d'approvisionnement se sont toutefois attardees a de petites zones d'echantillonnage comme des unites d'habitat individuelles. Pour combler ce manque de connaissances, nous avons applique un modele d'approvisionnement mecaniste a 22 troncons de cours d'eau longs de 100 a 400 m dans deux bassins versants du bassin du fleuve Columbia. Nous avons constate une forte correlation positive ([R.sup.2] = 0,61, p < 0,001) entre les capacites de charge predites et les densites de poissons observees. La proportion predite d'habitats convenables etait faiblement correlee a la densite de poissons observee ([R.sup.2] = 0,18, p = 0,051), mais le taux net moyen d'apport energetique predit dans les troncons echantillonnes n'etait pas une variable explicative significative de la biomasse de poissons observee. Nos resultats donnent a penser que la configuration spatiale de l'habitat, combinee a sa quantite et sa qualite, est un important determinant de l'utilisation de cet habitat. En outre, la capacite de charge predite par le modele s'avere prometteuse comme parametre de l'habitat. Nous avons egalement evalue la faisabilite d'appliquer cette approche de modelisation riche en donnees dans le cadre d'un programme de surveillance a grande echelle visant a examiner la qualite et la quantite des habitats. Bien que cette approche puisse etre couteuse sur le plan computationnel, nous estimons que la capacite du modele a integrer des parametres physiques de l'habitat (p. ex. profondeur, velocite) et des considerations biologiques importantes comme la disponibilite de nourriture et la temperature constitue un avantage qui compense amplement les couts associes. Nous croyons que cette approche de modelisation a beaucoup de potentiel comme outil pour aider a comprendre l'utilisation de l'habitat chez les poissons qui se nourrissent a la derive. [Traduit par la Redaction], Introduction Conservation and recovery of many lotic fishes depend on successful management and restoration of their habitat. In the Columbia River Basin (CRB), for example, recovery efforts for listed salmon [...]

Criteria used to characterize lotic salmonid habitat suitability are often based on correlations between physical habitat characteristics and salmonid abundance. Focusing on physical habitat features ignores other habitat components, such as an adequate food supply, that limit the amount of energy available for growth and survival. We tested the degree that food availability and temperature influence lotic salmonid consumption and growth rates and outline an approach for assessing habitat quality based on measurements of these features. We collected benthic and drifting invertebrate abundances, stream temperatures, and juvenile steelhead--rainbow trout (Onchorhynchus mykiss gairdneri) summer growth rates among nine stream segments in central Oregon. Stream temperatures and growth rates were used in bioenergetics model simulations to estimate O. mykiss consumption rates. The variation in O. mykiss consumption rates was explained by measurements of total drift biomass along a type II predator response curve ([R.sup.2] = 0.71). This simplified foraging relationship between food abundance and consumption is then used to estimate the consumption component of the bioenergetics model to allow estimation of salmonid growth potential. Validation of the growth potential model produced reasonably accurate estimates of fish growth rates at reaches within the study area and precise but biased estimates in novel systems. While additional reach-level habitat information may be required to make the model more generalizable, the assessment of invertebrate food availability offers a simple yet powerful approach for describing the growth potential of stream habitat. Les criteres utilises pour caracteriser la qualite des habitats de salmonides lotiques reposent souvent sur des correlations entre les caracteristiques physiques de l'habitat et l'abondance des salmonides. Cet accent mis sur les aspects physiques de l'habitat fait en sorte que d'autres elements de ce dernier qui limitent la quantite d'energie disponible pour la croissance et la survie, comme des ressources alimentaires adequates, ne sont pas pris en consideration. Nous avons verifie l'ampleur de l'influence de la disponibilite de nourriture et de la temperature sur les taux de consommation et de croissance de salmonides lotiques et proposons une approche pour evaluer la qualite de l'habitat reposant sur des mesures de ces caracteristiques. Nous avons recueilli des donnees sur l'abondance des invertebres benthiques et a la derive, la temperature du cours d'eau et les taux de croissance estivale de truites arc-en-ciel anadromes (Oncorhynchus mykiss gairdneri) dans neuf tronqons de cours d'eau du centre de l'Oregon. Les temperatures des cours d'eau et les taux de croissance ont ete utilises dans des simulations de modele bioenergetique afin d'estimer les taux de consommation d'O. mykiss. Les variations des taux de consommation d'O. mykiss s'expliquent par les mesures de la biomasse a la derive totale le long d'une courbe de reaction aux predateurs de type II ([R.sup.2] = 0,71). Cette relation d'alimentation simplifiee entre l'abondance de la nourriture et la consommation est ensuite utilisee pour estimer la composante de consommation du modele bioenergetique afin de permettre l'estimation du potentiel de croissance des salmonides. La validation du modele de potentiel de croissance produit des estimations raisonnablement exactes des taux de croissance des poissons dans les tronqons a l'interieur de la region a l'etude, ainsi que des estimations precises, bien que biaisees, dans de nouveaux systemes. Si des renseignements supplementaires sur l'habitat a l'echelle du tronqon pourraient etre necessaires pour produire un modele plus generalisable, l'evaluation de la disponibilite de nourriture invertebree constitue une approche simple, mais puissante pour decrire le potentiel de croissance dans des habitats lotiques. [Traduit par la Redaction], Introduction Increasing the understanding of salmonid ecology improves the approaches used to assess salmonid habitat suitability and leads to more effective prioritization of restoration and management activities. An abundance of [...]

Beaver are an integral component of hydrologic, geomorphic, and biotic processes within North American stream systems, and their propensity to build dams alters stream and riparian structure and function to the benefit of many aquatic and terrestrial species. Recognizing this, beaver relocation efforts and/or application of structures designed to mimic the function of beaver dams are increasingly being utilized as effective and cost-efficient stream and riparian restoration approaches. Despite these verities, the notion that beaver dams negatively impact stream habitat remains common, specifically the assumption that beaver dams increase stream temperatures during summer to the detriment of sensitive biota such as salmonids. In this study, we tracked beaver dam distributions and monitored water temperature throughout 34 km of stream for an eight-year period between 2007 and 2014. During this time the number of natural beaver dams within the study area increased by an order of magnitude, and an additional 4 km of stream were subject to a restoration manipulation that included installing a high-density of Beaver Dam Analog (BDA) structures designed to mimic the function of natural beaver dams. Our observations reveal several mechanisms by which beaver dam development may influence stream temperature regimes; including longitudinal buffering of diel summer temperature extrema at the reach scale due to increased surface water storage, and creation of cool—water channel scale temperature refugia through enhanced groundwater—surface water connectivity. Our results suggest that creation of natural and/or artificial beaver dams could be used to mitigate the impact of human induced thermal degradation that may threaten sensitive species. [ABSTRACT FROM AUTHOR]

Stream classification provides a means to understand the diversity and distribution of channels and floodplains that occur across a landscape while identifying links between geomorphic form and process. Accordingly, stream classification is frequently employed as a watershed planning, management, and restoration tool. At the same time, there has been intense debate and criticism of particular frameworks, on the grounds that these frameworks classify stream reaches based largely on their physical form, rather than direct measurements of their component hydrogeomorphic processes. Despite this debate surrounding stream classifications, and their ongoing use in watershed management, direct comparisons of channel classification frameworks are rare. Here we implement four stream classification frameworks and explore the degree to which each make inferences about hydrogeomorphic process from channel form within the Middle Fork John Day Basin, a watershed of high conservation interest within the Columbia River Basin, U.S.A. We compare the results of the River Styles Framework, Natural Channel Classification, Rosgen Classification System, and a channel form-based statistical classification at 33 field-monitored sites. We found that the four frameworks consistently classified reach types into similar groups based on each reach or segment’s dominant hydrogeomorphic elements. Where classified channel types diverged, differences could be attributed to the (a) spatial scale of input data used, (b) the requisite metrics and their order in completing a framework’s decision tree and/or, (c) whether the framework attempts to classify current or historic channel form. Divergence in framework agreement was also observed at reaches where channel planform was decoupled from valley setting. Overall, the relative agreement between frameworks indicates that criticism of individual classifications for their use of form in grouping stream channels may be overstated. These form-based criticisms may also ignore the geomorphic tenet that channel form reflects formative hydrogeomorphic processes across a given landscape. [ABSTRACT FROM AUTHOR]