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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.

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.

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.

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 (

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.

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.

The introduction of weirs into stream ecosystems resulted in modifications of serial continuity and in the decline of riverine fish species. Successful river restoration requires information on the ecological functionality of fish bypass channels that are considered an ecological improvement according to the European Water Framework Directive. In this study, we compared the functionality of three nature-oriented fish passes as compensatory habitats and migration corridors for fishes. Fish passes differed significantly from upstream and downstream reaches of the weirs, revealing higher current speed, lower water depth, smaller channel width and greater habitat variability. Following these structural differences, they provided key habitats for juvenile, small and rheophilic fishes that are typically underrepresented in highly modified water bodies. All fish passes were used as migration corridors, with increased fish movements during high discharge and at spawning periods. Because river stretches with high variability of current speed and water depth are scarce in highly modified water bodies, fish passes can play an important role as compensatory habitats and should thus be considered more intensively in habitat assessments and river restoration. Ideally, fish bypasses should mirror the natural discharge dynamics and consider all occurring fish species and sizes. Copyright © 2011 John Wiley & Sons, Ltd.

Summary 1. Most of the world’s rivers are affected by dams and weirs. Information on the quantitative and qualitative effects of weirs across biological communities is crucial for successful management and restoration of stream ecosystems. Yet, there is a lack of comprehensive studies that have analysed the serial discontinuity in direct proximity of weirs including diverse taxonomic groups from algae to fish. 2. This study compared the abiotic stream habitat characteristics upstream and downstream of weirs as well as their effects on the community structure of periphyton, aquatic macrophytes, macroinvertebrates and fish at five different study rivers. 3. Physicochemical habitat characteristics discriminated strongly between upstream and downstream sides of weirs in terms of water depth, current speed, substratum composition and the transition between free-flowing water and interstitial zone. Accordingly, abundance, diversity, community structure and functional ecological traits of all major taxonomic groups were indicative of serial discontinuity, but the discriminative power of individual taxonomic groups strongly differed between rivers. 4. The simultaneous inclusion of abiotic habitat variables, taxonomic diversity and biological traits in multivariate non-metric multidimensional scaling was most comprehensive and powerful for the quantification of weir effects. In some cases, the intrastream discrimination induced by weirs exceeded the variation between geographically distant rivers of different geological origin and drainage systems. Community effects were generally detectable on high levels of taxonomic resolution such as family or order level. 5.Synthesis and applications. River sections in spatial proximity to weirs are affected seriously and should be included in the ecological assessments of the European Water Framework Directive. Multivariate models that include several taxonomic groups and physicochemical habitat variables provide a universally applicable tool for the ecological assessment of impacts on serial discontinuity and other stressors on stream ecosystem health.

3,4-Methylenedioxymethamphetamine (MDMA)'s O-demethylenated metabolite, 3,4-dihydroxymethamphetamine (HHMA), has been hypothesized to serve as a precursor for the formation of toxic catechol-thioether metabolites (e.g., 5-N-acetylcystein-S-yl-HHMA) that mediate MDMA neurotoxicity. To further test this hypothesis, HHMA formation was blocked with dextromethorphan (DXM), which competitively inhibits cytochrome P450 enzyme-mediated O-demethylenation of MDMA to HHMA. In particular, rats were randomly assigned to one of four treatment groups (n = 9–12 per group): (1) Saline/MDMA; (2) DXM/MDMA; (3) DXM/Saline; (4) Saline/Saline. During drug exposure, time-concentration profiles of MDMA and its metabolites were determined, along with body temperature. One week later, brain serotonin (5-HT) neuronal markers were measured in the same animals. DXM did not significantly alter core temperature in MDMA-treated animals. A large (greater than 70%) decrease in HHMA formation had no effect on the magnitude of MDMA neurotoxicity. These results cast doubt on the role of HHMA-derived catechol-thioether metabolites in the mechanism of MDMA neurotoxicity. Synapse, 2011. © 2011 Wiley-Liss, Inc.