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Introduction: Hydropower plants are frequently equipped with physical and behavioral fish protection barriers to prevent downstream moving fish from harmful turbine passage and to guide them to alternative bypasses. As not only diadromous but also potamodromous fish species migrate and inevitably have to pass hydropower plants, knowledge on corridor usage for a wide range of species is important to identify potential deficits and to improve bypass efficiency.Methods: In this study, the corridor usage of downstream moving fish (6,646 individuals from 42 species) was investigated at four small-scale hydropower plants with different concepts to prevent turbine entrainment and to bypass fish.Results: Despite existing bypasses and fine screens with 15 mm and 20 mm bar spacing to prevent turbine entrainment, a large proportion of fish (35%–88%) still passed the turbines. The mainly poor efficiency of the investigated bypasses was probably due to low discharge and unfavorable bypass location or detectability. The various bypass types were used by a different range of fish species and sizes due to species-specific behavior and differing fish communities between sites. The effectiveness of the investigated downstream corridors was positively correlated with the share of discharge.Discussion: To reduce the negative ecological impacts of hydropower plants on downstream moving fish, well-performing bypasses are required that consider not only current requirements regarding design, dimensioning and location, but also the site-specific fish community. Thus, bypasses should function for the widest possible range of species, which can be achieved through less selective bypass types such as full-depth bypasses, or a combination of different bypass systems. Moreover, less harmful turbine technologies and more effective fish protection systems need to be implemented, since fine screens with 15 mm and 20 mm bar spacing cannot prevent small-bodied fish species and juvenile fish

European nase (Chondrostoma nasus) is a specialist riverine fish, characterised by a complex life cycle making it vulnerable to habitat degradation. Recent findings indicate that, analogously to salmonids, the interstitial zone quality may pose a serious bottleneck for successful recruitment of this species. In this study, nase eggs were exposed to different substrate qualities. First, standardised substrate mixtures with differing fine sediment additions were used. Second, we tested different homogenous gravel fractions for their influence on egg development and emergence success. In both setups, substrate composition significantly affected emergence success, timing of emergence and larvae size at emergence. In the substrate mixtures, emergence was most successful in substratum with no fine sediment addition (98%) and decreased to 55% in substratum with 20% fine sediment addition. Emergence was most successful in the coarsest fraction (93%) and decreased to 47% in the finest fraction. Over all treatments, the time between hatching and emergence from substrate differed by up to 156 degree days, thereby indicating that free embryos of nase use the shelter of the interstitial zone for early ontogeny. These results suggest that a loose and porous stream bed can positively contribute to the development success of eggs and larvae and thereby potentially improve the recruitment of nase populations. It is thus important to consider the substrate and interstitial conditions in the conservation and restoration management of this rheophilic cyprinid.

Floodplains were extensively altered by anthropogenic activities, resulting in modified flow dynamics essential for maintaining diverse riverine communities. There is growing interest in restoring environmental flows by artificially modulating discharge as a potential management option in regulated rivers. In the context of a large floodplain restoration project along the upper Danube, the effects of different magnitudes of discharge on fish, macroinvertebrates and macrophytes in different habitat types of the floodplain system were studied. Community composition of fishes and macroinvertebrates changed after peak-flows of up to a 20-fold increase of mean discharge, whereas species richness and coverage of macrophytes were hardly affected. Over all habitat types, similar community response patterns were evident for macroinvertebrates, whereas in fishes, the most pronounced changes occurred in floodplain ponds that only become connected to the main channel at high flows. Community changes for fish and macroinvertebrates were mostly attributed to higher numbers of individuals (3-fold increase for fishes) rather than to changes of species richness (maximum fish species richness change

Hydropower structures hinder the movement and migration of fishes, impairing their life cycles. Additionally, downstream moving fish are often at risk of being injured during turbine passage. To improve hydropower production towards more fish-friendly techniques and management, knowledge on timing and extent of natural patterns of fish downstream movement is necessary. So far, migration behaviour of long-distance migrators such as eel or salmon has been well studied, but little is known about seasonal and diurnal movement patterns of nonmigratory species or medium-distance migrators. In this study, movement patterns of 39 fish species captured by stownets while transiting hydropower facilities in four impounded rivers were assessed and compared with the fish community composition directly upstream of the hydropower plants assessed by electrofishing. Strong differences between the fish community composition inhabiting the upstream sides of the dams and the fish detected in downstream passage were evident. In each study river, the downstream moving fish community composition differed significantly between spring and autumn. On average, significantly more fish were caught during the night (2.9 fish/hr) than during the day (1.3 fish/hr). Topmouth gudgeon, European grayling and pike-perch mostly moved downstream during the night, whereas roach, spirlin and bleak were the most frequent downstream moving fish during daytime. Downstream fish movement was positively related with turbidity, water temperature and discharge. The strong differences in seasonal and diurnal fish movement patterns suggest that fish damage can be strongly reduced by adaptive turbine and corridor management, for example by shutting down turbines at peak movements.

Nitrate is an abundant nutrient and electron acceptor throughout Earth’s biosphere. Virtually all nitrate in nature is produced by the oxidation of nitrite by the nitrite oxidoreductase (NXR) multiprotein complex. NXR is a crucial enzyme in the global biological nitrogen cycle, and is found in nitrite-oxidizing bacteria (including comammox organisms), which generate the bulk of the nitrate in the environment, and in anaerobic ammonium-oxidizing (anammox) bacteria which produce half of the dinitrogen gas in our atmosphere. However, despite its central role in biology and decades of intense study, no structural information on NXR is available. Here, we present a structural and biochemical analysis of the NXR from the anammox bacterium Kuenenia stuttgartiensis, integrating X-ray crystallography, cryo-electron tomography, helical reconstruction cryo-electron microscopy, interaction and reconstitution studies and enzyme kinetics. We find that NXR catalyses both nitrite oxidation and nitrate reduction, and show that in the cell, NXR is arranged in tubules several hundred nanometres long. We reveal the tubule architecture and show that tubule formation is induced by a previously unidentified, haem-containing subunit, NXR-T. The results also reveal unexpected features in the active site of the enzyme, an unusual cofactor coordination in the protein’s electron transport chain, and elucidate the electron transfer pathways within the complex., The oxidoreductase (NXR) multiprotein complex is a key enzyme in the nitrogen cycle. A detailed structural and biochemical characterization of NXR from the anammox bacterium Kuenenia stuttgartiensis shows that this complex is a filament-forming protein that catalysers both nitrite oxidation and nitrate reduction, and elucidates the mechanisms governing complex assembly and function.

Many rivers in Central Europe are heavily affected by increased sedimentation due to erosion from agricultural land. High fine sediment loads can clog the interstitial system, increase turbidity, limit light penetration and potentially reduce primary productivity with negative impacts on stream biota such as reduced abundance and diversity. In this study, the effects of different erosion protection measures on instream sedimentation and the communities of fishes, macroinvertebrates and periphyton were evaluated. The erosion protection measures in the catchment successfully reduced the fine-sediment and nutrient input into the river system resulting in positive effects on interstitial habitat quality and the species assemblage of the assessed biota. The single taxonomic groups differed in their response both to catchment-related and instream-related variables. Fish community composition was best explained by catchment-scale variables, while periphyton and macroinvertebrate assemblage structure was significantly governed by instream-scale variables. For increasing restoration success, a combination of measures in the catchment area with structure-enhancing measures within the stream is necessary. The results also suggest that an integrative assessment of abiotic and biotic variables in monitoring increases the detectability of effects on the instream scale.

Freshwater fishes are among the most threatened groups of vertebrates, with 39% of all European fish species facing extinction. Herein, we provide a comprehensive analyses of historical data as well as fish monitoring data from 1989 through 2013 from Bavaria, Germany. The results of this study indicate that the most pronounced species-turnover already had occurred before the 1990s. Severe loss of species (21 out of 69 species lost until 1990s), decrease in spatial distribution (51 species, 27 reduced to Thymallus thymallus ), nase ( Chondrostoma nasus ), barbel ( Barbus barbus )), suggesting that effects of increasing water temperatures and increased fine sediment loads probably strongly contribute to the decline of those species. Our results generally confirmed the validity of current conservation status for most species, but also identified species (dace ( Leuciscus leuciscus ), chub ( Squalius cephalus ), trout ( Salmo trutta ) , minnow ( Phoxinus phoxinus ), nase and barbel) and habitats (medium-sized and large rivers) that deserve higher priority in conservation management. More consistent sampling of the same sites over years and a quantitative monitoring of environmental impact factors in appropriate spatial and temporal resolution is crucial to allow a future prioritization in freshwater fish conservation.

Amphetamine is a common therapeutic agent for alleviating the core symptoms associated with attention-deficit hyperactivity disorder (ADHD) in children and adults. The current study used a translational model of attention, the five-choice serial reaction time (5-CSRT) procedure with rats, to examine the time-course effects of d-amphetamine. Effects of different dosages of d-amphetamine were related to drug-plasma concentrations, fashioned after comprehensive pharmacokinetic/pharmacodynamic assessments that have been employed in clinical investigations. We sought to determine whether acute drug-plasma concentrations that enhance performance in the 5-CSRT procedure are similar to those found to be therapeutic in patients diagnosed with ADHD. Results from the pharmacokinetic/pharmacodynamic assessment indicate that d-amphetamine plasma concentrations associated with improved performance on the 5-CSRT procedure overlap with those that have been reported to be therapeutic in clinical trials. The current findings suggest that the 5-CSRT procedure may be a useful preclinical model for predicting the utility of novel ADHD therapeutics and their effective concentrations.

Significance Virophages are parasites of giant viruses within protists. They reduce giant virus production and increase host cell survival. They provide a defense system for protists against giant viruses in diverse environments, likely with ecological relevance for protist populations. To understand the remarkable virophage life cycle, it is crucial to investigate how they assemble into infectious particles and which processes require interactions with giant virus and host. We examined the marine virophage mavirus to show that its major and minor capsid proteins assemble into virus-like particles in the absence of specific host or viral factors. Subsequently, the virophage-encoded protease processes the major capsid protein to prepare virions for infection., Virophages have the unique property of parasitizing giant viruses within unicellular hosts. Little is understood about how they form infectious virions in this tripartite interplay. We provide mechanistic insights into assembly and maturation of mavirus, a marine virophage, by combining structural and stability studies on capsomers, virus-like particles (VLPs), and native virions. We found that the mavirus protease processes the double jelly-roll (DJR) major capsid protein (MCP) at multiple C-terminal sites and that these sites are conserved among virophages. Mavirus MCP assembled in Escherichia coli in the absence and presence of penton protein, forming VLPs with defined size and shape. While quantifying VLPs in E. coli lysates, we found that full-length rather than processed MCP is the competent state for capsid assembly. Full-length MCP was thermally more labile than truncated MCP, and crystal structures of both states indicate that full-length MCP has an expanded DJR core. Thus, we propose that the MCP C-terminal domain serves as a scaffolding domain by adding strain on MCP to confer assembly competence. Mavirus protease processed MCP more efficiently after capsid assembly, which provides a regulation mechanism for timing capsid maturation. By analogy to Sputnik and adenovirus, we propose that MCP processing renders mavirus particles infection competent by loosening interactions between genome and capsid shell and destabilizing pentons for genome release into host cells. The high structural similarity of mavirus and Sputnik capsid proteins together with conservation of protease and MCP processing suggest that assembly and maturation mechanisms described here are universal for virophages.

Floodplains have been strongly altered by human activities such as channelization and other river regulations. Globally, there is a growing interest in their restoration because of an increasing understanding of the ecological importance of these habitats for feeding, spawning, nursery or overwintering of aquatic species. In this study, a large floodplain restoration project of the upper Danube River was used to investigate colonization and succession patterns of fish, macroinvertebrates, macrophytes and periphyton in relation to abiotic habitat variables that can be restored through ecosystem management. Highest species diversity was detected near the contact zones of the floodplain channel to the main stem of the Danube, and in the transition zones of river sections (RS) and oxbow lakes (OS). The highest proportions of all taxa (82%) and of distinctive species (22%) were detected in RS, followed by OS (66% of all taxa, 8% distinctive species) and floodplain ponds (FP, 47% of all taxa, 5% distinctive species). The habitat types RS, OS and FP significantly differed in overall community composition and their colonization processes comprising fast colonization of current-adapted specialists in RS, and mostly generalist species in OS and FP. Our results indicate that restoration of floodplain habitats should not only consider the re-establishment of maximum connectivity, but also provide a mosaic of distinct habitat types with different degrees of connectivity and disturbance. Each habitat type in the floodplain supported a unique assemblage of species, which suggests that such habitat mosaics can facilitate exceptionally diverse ecosystems.

This study compares the effectiveness and representativeness of electrofishing, snorkelling, seining, baited lift netting, multi-mesh gillnetting, baited fish traps, fyke netting, angling and longline fishing, considering three typical lentic flood-plain habitats at different times of day. Electrofishing was by far the most effective method yielding highest species richness, species trait representation and catch per unit of effort (CPUE), followed by seining. For single species like dace Leuciscus leuciscus, European ruffe Gymnocephalus cernua, common bream Abramis brama and silver bream Blicca bjoerkna, seining was more effective than electrofishing. With both methods, some species were more consistently caught during night, dusk or dawn than during daylight. All other methods tested cannot be generally recommended for fish community assessments in shallow backwaters due to their low representativeness of species inventory and generally low CPUE. Based on these results, electrofishing of 30 m transect replicates at different times of day for monitoring the fish community in shallow backwaters, can be recommended, enabling the maximum possible comparability to adjacent river habitats. Seining should be considered as an alternative if accessibility of habitats is restricted or electrofishing is prohibited. The 25 species detected in the backwaters also suggest that these habitats contribute a large proportion of fish diversity and should be included in standard assessments of river ecological status.

Knowledge on the extent and mechanisms of fish damage caused by hydropower facilities is important for the conservation of fish populations. Herein, we assessed the effects of hydropower turbine passage on internal fish injuries using X-ray technology. A total of 902 specimens from seven native European fish species were screened for 36 types of internal injuries and 86 external injuries evaluated with a previously published protocol. The applied systematic visual evaluation of X-ray images successfully detected skeletal injuries, swim bladder anomalies, emphysema, free intraperitoneal gas and hemorrhages. Injuries related to handling and to impacts of different parts of the hydropower structure could be clearly distinguished applying multivariate statistics and the data often explained delayed mortality within 96 h after turbine passage. The internal injuries could clearly be assigned to specific physical impacts resulting from turbine passage such as swim bladder rupture due to abrupt pressure change or fractures of skeletal parts due to blade-strike, fluid shear or severe turbulence. Generally, internal injuries were rarely depicted by external evaluation. For example, 29% of individuals with vertebral fractures did not present externally visible signs of severe injury. A combination of the external and internal injury evaluation allows quantifying and comparing fish injuries across sites, and can help to identify the technologies and operational procedures which minimize harm to fish in the context of assessing hydropower-related fish injuries as well as in assessing fish welfare.

Fishes in European rivers are threatened by manifold stressors such as structural degradation, water pollution, overexploitation, land-use changes in the catchment, invasive species and global processes including climate change. Identifying main stressors in a stream/river system is of utterly importance for efficiently utilizing the scarce funds for conservation measures in order to achieve the best possible outcome. Within 203 headwater streams of Rhine, Elbe and Danube, we quantified the relative influence of different environmental stressors (water chemistry, food availability (macroinvertebrates), terrestrial predators) and anthropogenic stressors (land use, structural modification of streams) on fish assemblages at different spatial scales based on multivariate biota-environment models. In our analyses, the predictor variables percentage of impoundments, crop farming (especially erosion-prone crops such as maize) and ground sealing in the catchments, the number of wastewater treatment plants and biogas plants in the catchments as well as structural modifications of river banks were most often identified as stressors influencing fish community composition. However, the effects of the stressors varied between the investigated survey-area scales (two different catchments sizes and riparian strips) and regionally (entire study area, major drainage systems, river catchments, stream sizes, geographical subregions). In most cases, fish community composition was simultaneously affected by multiple stressors, underpinning the need for a more holistic and ecosystem-based approach in freshwater conservation and restoration.

Heavily modified water bodies (HMWB) are characterized by monotonous and straightened channel morphologies with high degrees of bank enforcement. They often lack shallow bank habitats, which are considered important for critical life stages of fishes. In this study, three principle options to engineer shallow stream zones were assessed concerning the value of the created habitats for larval, juvenile and adult stages of fishes in 30 sites from three HMWB. The construction scheme of the juvenile habitats comprised different degrees of embankment ranging from rip-rap structures with steep bank angles to almost nature-like construction schemes with very flat river-banks and sparing usage of structural enrichment such as boulders and dead wood. In general, the differences between the three habitat types were more pronounced in density of different life stages than in the presence or absence of species or certain life stages. A steep bank angle and a high degree of engineering such as placement of rip-rap embankment, boulders or dead wood structure in the habitats were hardly accepted by early larval and juvenile stages of rheophilic fishes. In contrast, the construction scheme of a nature-like habitat with a flat bank angle (

The hyporheic interstitial provides habitat for many different organisms – from bacteria to burrowing invertebrates. Due to their burrowing and sediment reworking behaviour, these ecosystem engineers have the potential to affect hyporheic processes such as respiration and nutrient cycling. However, there is a lack of studies that characterize the interactions between bioturbators, physico-chemical habitat properties and microbial communities in freshwater substrates. In a standardized laboratory experiment, we investigated the effects of three functionally different bioturbators, duck mussels (Anodonta anatina, Linnaeus 1758), mayfly nymphs (Ephemera danica, Muller 1764) and tubificid worms (Tubifex tubifex, Muller 1774), on the physico-chemical conditions and bacterial communities in hyporheic substrates. We hypothesized that different invertebrates distinctly alter habitat conditions and thus microbial community composition, depending on the depth and the manner of burrowing. A. anatina and E. danica caused an increase in interstitial oxygen concentration, whereas strong declines in oxygen concentration and redox potential were detected in the T. tubifex treatment. These effects on physico-chemical habitat properties were even detectable in open water. Mussels and tubificid worms also significantly influenced the composition of bacterial communities in the hyporheic zone. A loss or replacement of bioturbators in stream ecosystems due to anthropogenic habitat alterations is expected to result in shifts in microbial community compositions, with effects on nutrient fluxes, pollutant degradation and benthic food webs. An understanding of the effects of functionally different native and invasive bioturbators is crucial to predict changes in stream ecosystem functioning.

Photoacoutic imaging of biological tissues is characterized by depth dependent optical fluence loss and acoustic variations. Here, we aim to correct for these inaccuracies aided by extrinsic imaging priors obtained through concurrent high-frequency ultrasound (US) imaging of tissue samples. We segmented the skin line and characterized tissue components using deformable model-based segmentation from the ultrasound images. The prior information from co-registered US images and tissue temperature was used to accurately model light fluence and speed of sound respectively. Methods applied here show significant improvement in beamforming performance, enhanced visual image quality and a higher PSNR.

In contrast to the efforts made to develop functioning fishways for upstream migrants, the need for effective downstream migration facilities has long been underestimated. The challenge of developing well-performing bypasses for downstream migrants involves attracting the fish to the entrance and transporting them quickly and unharmed into the tailrace. In this study, the acceptance of different opening sizes of a surface bypass as well as the injuries which fish experience during the passage were examined. Overall bypass acceptance was low compared to the turbine passage. There was no significant difference in the number of downstream moving fish between the small and the large bypass openings. Across all fish species, no immediate mortality was detected. Severe injuries such as amputations or bruises were only rarely detected and at low intensity. Scale losses, tears and hemorrhages in the fins and dermal lesions at the body were the most common injuries, and significant species-specific differences were detected. To increase bypass efficiency, it would likely be useful to offer an alternative bottom bypass in addition to the existing surface bypass. The bypass injury potential could be further reduced by structural improvements at the bypass, such as covering protruding components.

Intensification of catchment land-use and the corresponding habitat degradation pose a threat to freshwater biodiversity and ecosystem health, yet few studies comprehensively quantified the effects of specific land-use variables on fish communities for different catchments within the same climatic region. Herein, we investigated the influence of catchment land use on fish community composition in the headwater areas of the European main river systems Elbe, Danube and Main/Rhine. The analyses comprising 289 streams and rivers in Bavaria, southern Germany, revealed that the influence of urbanization (e.g. ground sealing), potamalisation (impoundment of water courses), and erosion-prone, agricultural land-use types (e.g. root crop, maize) were significantly related to the fish community composition. In addition, multiple stressors were effective indicators and their importance differed between survey-area scales, geographical regions, and stream sizes. The findings suggest that terrestrial effects of land-use and urbanization need to be more strongly considered in the conservation of endangered stream fishes, ideally including combined measures of erosion control, restoration of environmental flows and mitigation of structural degradation.

Modification of streams and rivers has mediated range expansions of several species into areas beyond their natural distribution. In this study, a newly created secondary floodplain channel (SFC), with three connections to the Danube, was used as a model system to compare colonisation by indigenous versus non-indigenous species of macroinvertebrates. Three years after the opening of the channel, it was colonised by 210 taxa. Indigenous species were more abundant than non-indigenous ones, both in the channel as well as in the Danube, and colonisation was mostly determined by habitat characteristics. In non-indigenous species, proximity to the source habitat was the main explanatory variable. Non-indigenous colonisers mostly had indifferent functional traits, in contrast to indigenous macroinvertebrates. These differences were particularly pronounced in amphipods where an equal number of five species per group occurred. The results of this study suggest that the factors determining colonisation patterns of indigenous versus non-indigenous species with similar dispersal abilities can strongly differ. Consequently, the creation of specific habitat structures (gravel-dominated, high current flow, bank vegetation) in restoration of floodplain channels can increase competitiveness of native species valued in conservation, particularly if sufficiently long channels with limited edge effects to the source habitat are built.

River floodplains are important for their biodiversity and productivity, yet are considered one of the most threatened ecosystem types. Due to increasing awareness of the ecosystem services provided by floodplains, their restoration and reconnection with the main channels have become core topics in policy, management and science. In one of the last remaining alluvial forests at the upper Danube River, a new secondary floodplain channel was artificially created in 2010 using a nature-orientated construction scheme. The objective of this study was to analyze the colonization and succession of the fish community in the new floodplain river and the adjacent temporarily connected floodplain habitats over a period of four years. Following the restoration-induced changes in habitat morphology and availability of habitat space, a very fast initial colonization was observed, with 46% of the source species pool of the Danube present in the study area after only two months. Colonization by fishes was explained by habitat features such as habitat morphology as well as biological features such as the species inventory of the source habitat and life-history traits. The time span required for developing functional demographic structures could be explained by the degree of specialization in different life stages, with faster population development in species with high ecological plasticity. The high representation of small individuals in multiple fish species indicates the importance of the artificial floodplain channel as habitat for early life stages. Consequently, the new floodplain channel seems to at least partly mitigate the habitat loss in the main river.

Modeling of fish population developments in the context of hydropower impacts and restoration planning requires autecological information on critical life stages (especially on juvenile stages and reproduction). We compiled and examined the current data availability in peer-reviewed and grey literature on autecological requirements of ten rheophilic fish species at risk, belonging to the salmonid, cyprinid, and cottid families. In total, 1725 data points from 223 sources were included. Economically important salmonids and the common nase were the most studied species. Grey and peer-reviewed data showed similar dispersion and variance and contributed nearly equally to the data pool of the specific species. An in-depth analysis on seven ecological parameters revealed no significant differences between both sources in terms of data availability and quality. We found substantial deficits in the data for about a quarter of the reviewed ecological parameters, in particular on individual densities in the habitats, egg development and information about juvenile stages despite the necessity of such data for more advanced population analyses. To secure fish populations in the long term, more data on basic autecological parameters is needed and grey literature might add valuable information, particularly if it relies on standardized methodologies.

Stream substratum plays a key role for many riverine species and has become a focus topic in the context of structural habitat improvements. There is a lack of studies that compare the effectiveness of different substratum restoration measures. Herein, we compare four restoration techniques (two different gravel introductions, substratum raking and sickle-formed constrictor) that were carried out in six replicate rivers. Each measure was monitored for changes in physicochemical substratum quality and the effects of the construction work on downstream sites. Generally, the effects on physicochemical substratum quality were highly variable between restoration types and rivers and strongly decreased within 1 year. Most pronounced changes of substratum quality were detected for the gravel introductions. Substratum raking and the sickle-formed constrictor had the smallest effects, which were dependent on the original substratum composition of the restored sites. At the same time, substratum raking caused an average fine sediment deposition of 17 kg m−2 on downstream sites, being sixfold higher than for the other measures. Consequently, all of the investigated substratum restoration techniques are confined to short-term improvement of substratum quality. This finding, together with the observed damage on downstream sites, suggests that a rethinking of the currently applied restoration techniques is required, better considering catchment and natural substratum dynamics in river restoration. Copyright © 2014 John Wiley & Sons, Ltd.

Stream restoration is widely applied for conservation of freshwater ecosystems, but systematic comparisons on the effects of different techniques are rare. In this study, we systematically evaluated two types of gravel introduction, substratum raking and the placement of boulders in six streams. We compared indicator-based and multi-scale approaches that simultaneously assess effects on target species, different taxonomic groups and on ecosystem scale. Gravel introduction had by far the strongest effects on macroinvertebrates (increase of species density and numbers of individuals), periphyton (increase of cell numbers) and macrophytes (decrease of coverage, species numbers and biomass), followed by substratum raking. The placement of boulders had no significant long-term effects on aquatic communities. Over all investigated restoration treatments, fish community composition only changed significantly in 50% of the study rivers depending on the occurrence of species sensitive to the structures introduced by the restoration treatments. These were lithophilic, rheophilic and invertivorous fishes, comprising several species listed in the Red List of endangered species, which used the added 16–32 mm gravel as juvenile habitat. Areas with introduced gravel were also most frequently used by spawning Salmo trutta , Thymallus thymallus and Phoxinus phoxinus . In contrast, active bioindication using Salmo trutta eggs indicated that none of the restoration treatments was sufficient to enhance habitat conditions in deeper substratum layers throughout the egg incubation period. Our results suggest that instream restoration measures can contribute to freshwater biodiversity conservation, but reproductive success of species depending on long-term improvement of interstitial water quality cannot be achieved without considering catchment effects and natural substratum dynamics.

Taxonomic sufficiency (TS) has been proposed for assessing community composition and environmental impacts as a way to balance the need to indicate the biology of the organisms present with time and effort needed for species identification. TS has been applied most often to marine and freshwater macroinvertebrates, but tests of its usefulness are lacking for other freshwater groups. We analyzed the effects of taxonomic resolution, functional groupings, and data transformation on multivariate community patterns in periphyton, macrophytes, macroinvertebrates, and fishes, and on the quantification of biodiversity and environmental gradients. The applicability of TS differed strongly among taxonomic groups, depending on the average taxonomic breadth of the species sets. Numerical data resolution had more pronounced effects on community patterns than taxonomic resolution. Richness was strongly affected by data aggregation, but diversity indices were statistically reliable up to order level. Taxonomic a...

The current study aimed to elucidate the role of pharmacokinetic (PK) parameters and neurotransmitter efflux in explaining variability in (±) 3, 4-methylenedioxymethamphetamine (MDMA) self-administration in rats. PK profiles of MDMA and its major metabolites were determined after the administration of 1.0 mg/kg MDMA (iv) prior to, and following, the acquisition of MDMA self-administration. Synaptic levels of 5-hydroxytryptamine (5HT) and dopamine (DA) in the nucleus accumbens were measured following administration of MDMA (1.0 and 3.0 mg/kg, iv) using in vivo microdialysis and compared for rats that acquired or failed to acquire MDMA self-administration. Effects of the 5HT neurotoxin, 5,7 dihydroxytryptamine (5, 7-DHT), on the acquisition of MDMA and cocaine self-administration were also determined. In keeping with previous findings, approximately 50% of rats failed to meet a criterion for acquisition of MDMA self-administration. The PK profiles of MDMA and its metabolites did not differ between rats that acquired or failed to acquire MDMA self-administration. MDMA produced more overflow of 5HT than DA. The MDMA-induced 5HT overflow was lower in rats that acquired MDMA self-administration compared with those that did not acquire self-administration. In contrast, MDMA-induced DA overflow was comparable for the two groups. Prior 5,7-DHT lesions reduced tissue levels of 5HT and markedly increased the percentage of rats that acquired MDMA self-administration and also decreased the latency to acquisition of cocaine self-administration. These data suggest that 5HT limits the initial sensitivity to the positively reinforcing effects of MDMA and delays the acquisition of reliable self-administration.

In this study, a comparison of point abundance sampling (PAS) electrofishing, angling with two different hook sizes and trap-based fishing was performed in a non-wadeable river to analyse their effects on catch per unit effort (CPUE) and population characteristics of invasive round goby Neogobius melanostomus. PAS electrofishing was identified as the most effective (mean ± s.e. CPUE = 57 ± 4 N. melanostomus min(-1) ) and least selective method in terms of size, feeding status and species composition. Angling had the second highest CPUE, but was more size selective and resulted in a higher proportion of males compared to electrofishing [overall sex ratio angling (female:male) = 1:0.92, electrofishing 1:0.65]. Owing to low CPUE (0.012 ± 0.004) and low frequency of occurrence, minnow traps were least suitable for N. melanostomus population assessment. The results of this study suggest that a higher degree of standardization and inter-calibration is useful to achieve better comparability of population data of invasive N. melanostomus and other benthic fish species.

Hydropower plants have been linked with high mortality and passage impairments during Silver Eel (Anguilla anguilla) downstream migration, but there is still a lack of effective and economically viable management options for safe power plant passage. This study used an Adaptive Resolution Imaging Sonar (ARIS) to investigate how undershot sluice gate management at a small-scale hydropower plant affects Silver Eel behavior during downstream migration. Not a single eel out of 1323 counts used the eel bypass system, which is currently considered a technical standard. Instead, Silver Eels approached the opening of an undershot sluice gate and effectively used this corridor during their downstream migration. The opening size of the undershot sluice gate and the resulting higher current velocities in front of this corridor were identified as the most important triggers. Migration occurred primarily at night and peaked with rising discharge. This study suggests that undershot sluice gates can be used as a cost-effective downstream migration pathway and should be operated at night on rising discharge during the peak migration period for eels.