Search

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 [...]

A geomorphic assessment of the Middle Fork John Day Watershed, Oregon, USA, was used to generate a hierarchical, map-based understanding of watershed impairments and potential opportunities for improvements. Specifically, we (1) assessed river diversity (character and behavior) and patterns of reach types (and their controls); (2) evaluated the geomorphic condition of the streams; (3) interpreted their geomorphic recovery potential; and (4) synthesized the above into a hypothetical, strategic management plan. Collectively, these maps can set bounds and provide realistic guidance for river rehabilitation, design and implementation efforts. Fifteen distinct reach types were identified, two-thirds of which are found along perennial streams. On the basis of a variety of geo-indicators, approximately two-thirds of all perennial stream reaches were found to be in ‘good’ geomorphic condition, whereas one-third had departed to ‘moderate’ and ‘poor’ condition. Departures from ‘good’ condition were primarily related to riparian vegetation removal, conversion of floodplain to agricultural land uses (farming and grazing), logging, and channel bed dredge mining for gold. Encouragingly, the majority of reaches classified as being in moderate geomorphic condition were found to have high recovery potential. While our geomorphic assessment has practical utility for informing physically realistic expectation management for efforts like salmonid habitat restoration, the maps themselves are the key vehicle for communicating and visualizing among stakeholders. [ABSTRACT FROM PUBLISHER]

This corrects the article DOI: 10.1038/srep28581 [ABSTRACT FROM AUTHOR]