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 [...]

Prioritizing restoration opportunities effectively across entire riverscape networks (i.e., riverine landscape including floodplain and stream channel networks) can be difficult when relying on in‐channel, reach‐scale monitoring data, or watershed‐level summaries that fail to capture riverscape heterogeneity and the information necessary to implement restoration actions. Leveraging remote sensing and geospatial tools to develop spatially continuous information across nested hierarchical scales may support increased understanding of local riverscape reaches in their broader network context. Using riparian (vegetation) and geomorphic (elevation) indicators to assess status of riverscape health, along with a measure of restoration capacity (valley bottom area), could be adapted to fit specific management goals related to riverscape restoration. Frameworks using remotely sensed vegetation and elevation data to prioritize restoration continuously across riverscapes at restoration‐relevant, reach‐scales may uphold the ecosystem services provided by riverscapes. By incorporating local knowledge and identifying caveats for using these datasets, continuous inferences can be applied at network scales (watershed to regional extent and reach‐scale resolution) to prioritize restoration over a wide variety of ecoregions. This article is categorized under:Water and Life > Conservation, Management, and AwarenessWater and Life > MethodsWater and Life > Stresses and Pressures on Ecosystems [ABSTRACT FROM AUTHOR]

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 [...]

Stream ecosystems can be dramatically altered by dam‐building activities of North American beaver (Castor canadensis). The extent to which beavers' ecosystem engineering alters riverscapes is driven by the density, longevity, and size (i.e. height and length) of the dams constructed. In comparison to the relative ubiquity of beaver dams on the landscape, there is a scarcity of data describing dam heights. We collected data describing dam height and dam condition (i.e. damaged or intact) of 500 beaver dams via rapid field survey, differentiating between primary and secondary dams and associating each dam with a beaver dam complex. With these data, we examined the influence of beaver dam type (primary/secondary), drainage area, streamflow, stream power, valley bottom width, and HUC12 watershed on beaver dam height with linear regression and the probability that a beaver dam was damaged with logistic regression. On average, primary dams were 0.46 m taller than secondary dams; 15% of observed dams were primary and 85% secondary. Dam type accounted for 21% of dam height variation (p <0.0001). Slope (p = 0.0107), discharge (p = 0.0029), and drainage area (p = 0.0399) also affected dam height, but each accounted for less than 3% of dam height variation. The average number of dams in a dam complex was 6.1 (SD ± 4.5) and ranged from 1 to 21. The watershed a beaver dam was located in accounted for the most variability (17.8%) in the probability that a beaver dam was damaged, which was greater than the variability explained by any multiple logistic regression model. These results indicate that temporally dynamic variables are important influencers of dam longevity and that beaver dam ecology is a primary factor influencing beaver dam height. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Spatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. Conceptual models predict that in situ primary production should vary with river characteristics, but the influence of autochthonous resource availability on the capacity for river reaches to support fish is poorly understood. We estimated primary production throughout the South Fork and Middle Fork of the John Day River, Oregon, by measuring diel cycles in dissolved oxygen (DO) during July 2013. Using these data, we (1) evaluated the extent to which juvenile salmonid abundance and resource limitation correlated with areas of high gross primary production (GPP), (2) developed models to predict GPP from both site-level measurements and remotely sensed data, and (3) made predictions of GPP across the entirety of theMiddle Fork John Day River (MFJD) network and assessed the utility of these spatially continuous predictions for describing variation fish densities at broad scales. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources. Estimates of GPP across fish sampling sites explained, on average, 58-63% of the variation in juvenile salmonid densities during the summer sampling period, and 51-83% during the fall sampling period, while continuous network predictions of GPP explained 44% of the variation in fish densities across 29 km of the MFJD. Further, GPP explained nearly half of the variation in juvenile steelhead dietary resource limitation, as inferred from bioenergetics modeling results. These results comprise a first effort at quantifying variation in autochthonous production across an entire river network and, importantly, provide a much-needed food-web context for guiding more effective fish and habitat management. [ABSTRACT FROM AUTHOR]

Closed population models are commonly used to estimate stream salmonid abundances using mark–recapture information collected during electrofishing surveys. To meet the model assumption of geographic closure, block nets are often used to prevent emigration and immigration of fish during the survey. Increased sampling and tagging efforts in an open site may be an appealing trade-off given the time it takes to properly deploy block nets, but it also increases an abundance estimate’s vulnerability to bias. We assessed the extent of geographic closure violation from emigration in open sites between mark and recapture passes utilizing PIT antennas as virtual block nets. This allowed us to quantify emigration rates of juvenile steelheadOncorhynchus mykissfrom 60 fish surveys across multiple seasons and watersheds. Our goals were to determine how season and site length influence emigration, examine how the life history of an anadromous salmonid may induce bias on mark–recapture abundance estimates, and provide recommendations on minimizing the bias associated with violating the geographic closure assumption. Average emigration rate was low across all surveys and watersheds (5.1%), with higher emigration rates correlating with larger fish, shorter site length, and the season in which the site was sampled. We concluded that the bias associated with violating the geographic closure assumption in an open site can be minimized by avoiding times of migration and by sampling sites up to 650 m long depending on fish density and capture efficiency. Our findings provide useful information for planning mark–recapture studies that have multiple sampling objectives. Received July 27, 2016; accepted May 24, 2017Published online August 4, 2017 [ABSTRACT FROM AUTHOR]

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]

Despite substantial effort and resources being invested in habitat rehabilitation for stream fishes, mechanistic approaches to designing and evaluating how habitat actions influence the fish populations they are intended to benefit remain rare. We used a net rate of energy intake (NREI) model to examine expected and observed changes in energetic habitat quality and capacity from woody debris additions in a 40 m long study reach being treated as part of a restoration experiment in Asotin Creek, Washington. We simulated depths, velocities, and NREI values for pre-treatment, expected, and post-treatment habitat conditions, and we compared pre-treatment versus expected and pre-treatment versus post-treatment simulation results. The pre-treatment versus expected topography simulations suggested treatment would increase energetically favorable area, mean NREI, and capacity in the study reach. Pre-treatment versus post-treatment comparisons yielded similar predictions, though to smaller magnitudes, likely due to the short time span and single high-flow event between pre- and post-treatment data collection. We feel the NREI modelling approach is an important tool for improving the efficacy of habitat rehabilitation actions for stream fishes. [ABSTRACT FROM AUTHOR]

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]

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]

We conducted simulations to compare the precision and bias of survival estimates from Cormack–Jolly–Seber (CJS) and Barker models to known parameter values based on empirical data for steelhead/resident Rainbow TroutOncorhynchus mykissfrom the John Day River, Oregon. We simulated seasonal differences in recapture and survival rates, and we varied the number of fish tagged, recapture and resight rates, sample site size, and fish movement (migratory or resident). Survival estimates from the Barker model had higher precision and lower or equal bias in comparison with estimates from the CJS model under almost all simulation scenarios. The precision of Barker survival estimates increased the most as the number of tagged fish increased from 50 to 200 (CV = 0.4–0.09). The Barker model's superior performance was dependent on the availability of resight data; such data are becoming more readily available, especially in places where large numbers of individuals are PIT-tagged and where an interrogation infrastructure exists (e.g., Columbia River basin). Tagging of 75–100 fish/site during high-capture periods (e.g., summer and fall) and focusing on the resighting of fish with fixed or mobile interrogators during low-capture periods (i.e., winter and spring) may be the most cost-effective strategy for improving estimates of juvenile steelhead survival. Received April 18, 2014; accepted August 26, 2014 [ABSTRACT FROM AUTHOR]

The loss of both habitat quality and quantity for anadromous fish in the Columbia River basin has been identified as a major factor in the decline of many species and has been linked to a variety of land management activities. In this study, we compared stream reaches in watersheds representing both managed and reference conditions to determine whether we could detect differences in physical habitat variables. We divided stream habitat measures into three components: stream banks, instream habitat (pools and pool depth), and stream substrate. We randomly sampled perennial streams within 261 sixth hydrologic unit code (HUC) stream reaches on federal lands in Idaho, Montana, Oregon, and Washington. The sample population represented stream reaches in 62 reference watersheds and 199 managed watersheds. An unbalanced, incomplete-block-design analysis of covariance (ANCOVA) was performed on each of the habitat variables using geology type as the block effect and bank-full width, stream gradient, and average precipitation as the covariates. Watersheds containing reference stream reaches had a slightly higher percentage of federal lands, were smaller, tended to occur at higher mean elevations, and received more annual precipitation than did the managed watersheds. We observed differences in most measures of stream habitat between reference and managed watersheds, generally in the direction we expected. Stream banks were more stable and more undercut in reference stream reaches. Pools in reference stream reaches were deeper than pools in managed stream reaches and had less fine sediment in pool tails. Analysis of covariance was an effective way to compare data across a large, relatively heterogeneous landscape where sample site stratification may be impractical or sample sizes are limited. We believe that the comparison of reference conditions to conditions across managed landscapes provides a credible way to report on the condition of these systems in lieu of trend... [ABSTRACT FROM AUTHOR]

Bonneville cisco Prosopium gemmifer are endemic to and found only in Bear Lake, Utah-Idaho. As part of an investigation into life history characteristics of this species of special conservation concern, we examined survival of Bonneville cisco eggs by measuring changes in egg density under natural environmental conditions. Eggs were vacuumed off the lake bottom over a month period in 1992 and 1993. This survey indicated that egg loss was high: fewer than 4% of the eggs remained after 30 d of an incubation period lasting more than 100 d. Thirty percent of this egg loss could be explained by unsuccessful fertilization or improper embryonic development. An exclosure experiment demonstrated, however, that the majority of the Bonneville cisco egg loss was due to fish predation. A second exclosure experiment indicated that predation rates were not affected by changes in egg density. Our results suggested that fish predation on the eggs may determine recruitment success of Bonneville cisco. [ABSTRACT FROM AUTHOR]

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