Hydrobiologia

Schludermann, E.; Liedermann, M.; Hoyer, H.; Tritthart, M.; Habersack, H.; Keckeis, H.

doi: 10.1007/s10750-013-1680-9pmid: N/A

The effects of navigation on young-of-the-year (YOY) fish were investigated for the Danube River based on an integrative approach. During YOY growing season, wave height, wave frequency and water currents were recorded. Synchronously, fish drift and fish abundance of YOY were monitored in two distinct inshore nursery habitats—a gravel bar and a groyne field. The characteristics of vessel-induced waves were correlated to YOY-drift. In both habitats, an increase in drift densities during ship passages was observed. At the same time, assemblage composition and drift densities differed between habitat types. At the gravel bar, drift densities of larval cyprinids—representing many keystone species of the Danube—were higher during ship passages. In the groyne field, drift was low and percids dominated the YOY-assemblage along the shore. Banks with gentle slopes in the main channel seem to be particularly affected by vessel-induced wave wash. Precisely such habitats are often established within the scope of modern river restoration projects because they provide suitable nursery habitats for riverine fish species. Beside the positive effects on biota, the establishment of these habitats in navigable reaches may create problems for YOY-fish due to displacement effects induced by ship-generated waves.

Habersack, H.; Tritthart, M.; Liedermann, M.; Hauer, C.

doi: 10.1007/s10750-012-1429-xpmid: N/A

Habitat modelling has become an increasingly important tool in river sciences to evaluate impacts on running waters and to predict the effects of river restoration in the context of the European Water Framework Directive which aims to reach a good ecological status by 2015. In a scaling framework like the River Scaling Concept, micro- and mesoscale habitat modelling hierarchically integrate point-/local-scale abiotic processes like grain sorting, initiation of sediment transport, bedform development and braiding with biological processes like spawning, daily and seasonal movements, feeding and shifting to refuge habitats. The paper, along with application results, shows that micro- and mesoscale habitat models are complementary especially for large river systems. Overall possibilities, restrictions and future development are discussed. Both rely on dynamic abiotic modelling as a basis as well as on biological data. In future, especially for large rivers, habitat modelling should be addressed on both scales (micro-/meso-) with the main focus on site-specific efficiencies (e.g. minimum efforts) and uncertainties (e.g. transferring suitability indices).

Schmutz, Stefan; Kremser, Helga; Melcher, Andreas; Jungwirth, Mathias; Muhar, Susanne; Waidbacher, Herwig; Zauner, Gerald

doi: 10.1007/s10750-013-1511-zpmid: N/A

Large rivers are worldwide under severe pressure and there is a lack of information on large river restoration. The present paper represents a meta-analysis of available data on river rehabilitation projects performed at the Austrian Danube River consisting of six rehabilitation projects addressing 19 sites. The overall goal was to analyse the response of fish assemblages to different rehabilitation types based on (1) morphological type (“Instream Habitat Enhancement”, “backwater Enhancement”, “extended Enhancement”), (2) length of rehabilitation measure (3) time after construction (4) applied monitoring design. Biological metrics evaluated included number of fish species and relative density, habitat guilds and Leitbild species. In total, number of species increases by 55% comparing rehabilitated with unrestored sites. The number of species of all habitat guilds is higher after rehabilitation. The proportion of rheophilic species increased and the community evolved toward a more type-specific community, according to the Leitbild. Significant differences between measure types were not detected. The rehabilitation success depends mainly on its spatial extent. Highest positive response of number of rheophilic species is achieved by a length >3.9 km. The results show that habitat rehabilitation of large rivers is effective if the spatial extent of the measure is in accordance with river size.

Keckeis, Hubert

doi: 10.1007/s10750-013-1485-xpmid: N/A

The rip-rap along an approx. 3-km-long shore in the main channel of the River Danube in Austria was completely removed to initiate the formation of a river bank through natural erosional and depositional processes. This study aimed to determine the short-term effect of this restoration measure on species composition and abundance of different developmental stages of fish at two spatial scales (micro- and mesohabitat). For this purpose, changes in abundance of early stages, as well as assemblage structure and species diversity of the benthic and the sub-littoral fish community were studied before and after restoration. No significant effects of restoration measures on the benthic fish assemblage were found. Significant and contradictory effects of the measures on the early stages and on the sub-littoral assemblage were observed. The abundance of fish larvae decreased after restoration, and this change could be attributed to the generally higher flow velocities in the new inshore microhabitats. Simultaneously, the species number and the abundance of fishes from the sub-littoral assemblage increased after restoration. This study has found that the main channel of the Danube still contain a high fish species diversity, and potentially plays a crucial role in recruitment of characteristic fluvial fishes.

Loisl, Franz; Singer, Gabriel; Keckeis, Hubert

doi: 10.1007/s10750-013-1588-4pmid: N/A

Fish assemblages in large rivers are highly diverse communities. However, a single method to describe these complex systems adequately is not available as of yet. In this paper we propose a combination of normalized catch-per-unit-effort data of three fish sampling methods, thus providing a more inclusive representation of the overall assemblage. We investigate fish species occurrence and abundance in a survey at three consecutive sites in the free-flowing main channel of the Austrian Danube east of Vienna. Using boat and wading electrofishing, as well as longline fishing we collected data in four mesohabitats at each site. We analysed richness, assemblage structure and abundance of single species and tested site and mesohabitat as differentiating forces on the fish assemblage structure, applying PERMANOVA and NMDS. The investigated sites are populated by a species-rich fish assemblage, of which we collected a total of 36 species. The composition of the assemblage was rather consistent except for the occasional occurrence of rare species. At the smaller mesohabitat scale, however, the assemblages differed considerably and hydromorphological conditions were apparently the major structuring force. Overall, the combination of methods considerably improves the assessment across sites and mesohabitats and contributes to our understanding of large river fish assemblages.

Plum, Nathalie; Schulte-Wülwer-Leidig, Anne

doi: 10.1007/s10750-012-1433-1pmid: N/A

After presenting some key data about the River Rhine, the main problems, tasks and the structure of the International Commission for the Protection of the Rhine (ICPR) as an intergovernmental organization are explained. Right up to the 1970–1980s, the river was so heavily polluted with wastewater that it was generally called the sewer of Europe (ICPR, A Programme for Migratory Fish in the Rhine System 2004, Kobl enz, 2004). Some milestones—disasters and resulting programmes—in the history of the ICPR are shown, following the main topics of the ICPR work: water quality, ecology, flood protection and climate change. The main outcomes of the programmes are presented and linked with European Directives. It is shown how the achievements of the Rhine Commission have triggered the development of directives at European level, such as the Water Framework Directive (2000) and the Directive on Flood Assessment and Management (2007). Finally, positive and negative experience is reconsidered and factors for a successful transboundary river basin management are pointed out against the background that other river basin co-operations starting their work today could share the lessons learnt by the ICPR.

Schipper, Aafke; Hendriks, A.; Ragas, Ad; Leuven, Rob

doi: 10.1007/s10750-013-1521-xpmid: N/A

Floodplains of large rivers are among the most dynamic and diverse, yet most threatened ecosystems on earth. For a solid underpinning of river conservation and rehabilitation measures, it is critical to unravel the influences of the multiple stressors affecting floodplain ecosystems. Using canonical correspondence analysis with variance partitioning, we disentangled and ranked the influences of three floodplain ecosystem stressors (land use, flooding and soil contamination) on terrestrial plant and soil-dwelling arthropod assemblages in a floodplain area along the river Rhine in The Netherlands. We included five biotic assemblages: plant species (73 taxa), ground beetle species (57 taxa), ground beetle genera (29 taxa), beetle families (32 taxa) and arthropod groups at taxonomic levels from family to class (10 taxa). Plant and arthropod assemblages were primarily related to land use, which explained 19–30% of the variation in taxonomic composition. For plant species composition, flooding characteristics were nearly as important as land use. Soil metal contamination constituted a subordinate explanatory factor for the plant assemblages only (3% of variation explained). We conclude that the taxonomic composition of terrestrial plant and arthropod assemblages in our study area is related to land use and flooding rather than soil metal contamination.

Rakowitz, Georg; Berger, Bernhard; Schludermann, Elisabeth; Tritthart, Michael; Habersack, Helmut; Keckeis, Hubert

doi: 10.1007/s10750-013-1594-6pmid: N/A

Danube main channel deep pools are in-stream habitats of high ecological relevance. We used dual-frequency identification sonar to investigate seasonal and diel fish abundance in two hydrodynamically different deep pools in the main channel of the Danube River in 2008. In general, fish of different species were present in both deep pools throughout the year, irrespective of water level. High fish abundance was recorded during autumn and winter, low abundance during spring and summer. During low discharge and low temperature and particularly during low flow velocity, low kinetic energy and low shear stress, high fish abundance in densely packed aggregations were observed, a clear indication for the refuge capacity of deep pools. In contrast, during turbulent hydraulic conditions with high flow velocity, high turbulent kinetic energy and high shear stress, low fish abundance occurred, mainly consisting of single fish, small fish shoals and benthic fish specimens. Furthermore, we could reveal that calm as well as turbulent pools fulfil the requirements as refuge and feeding habitat of eurytopic, piscivorous catfish throughout the year. The application of a multiple linear model based on the hydrological parameters discharge and water temperature as well as the hydraulic parameters flow velocity, turbulent kinetic energy and shear stress provided highly significant evidence between the observed and the expected seasonal fish abundance in the deep pools (R 2 = 0.77, P < 0.001). For the first time these results make clear that the main channel deep pools are important refuge and resource habitats of different species of the Danube fish community. Deep pools are key habitats for the in-stream fish community of the Danube River.

Schletterer, M.; Füreder, L.; Kuzovlev, V.; Zhenikov, Y.; Grigorieva, I.

doi: 10.1007/s10750-013-1466-0pmid: N/A

The Volga, the largest river in Europe, has experienced multiple stressors from human activities. Recently we showed that its upper course (about 500 km, from its source to Tver) still has large sections with low impact and a natural type-specific potamal flora and fauna. Our present research in the East European lowlands aim to define reference conditions for mid-sized to large lowland rivers in order to build a basis for future management and conservation. Three monitoring sites were selected based on the results from intensive sampling in 2005. In subsequent field campaigns between 2006 and 2010 regular surveys were carried out each year in summer and additional ones in spring. A taxon-rich macroinvertebrate fauna, including several rare potamal relict species, was recorded and the data was used to provide an overview of annual and interannual variation in community indices and metrics. The conditions described for the headwaters of the Volga River system can be used as a reference state for medium-sized and large lowland rivers in regions where reference sites of these types are lacking.

Dokulil, Martin

doi: 10.1007/s10750-013-1589-3pmid: N/A

Autochthonous production of potamoplankton has recently attracted greater interest as it was incorporated into expanded river concepts such as the flow pulse concept or the riverine productivity model (RPM). This review assembles data on primary production from the River Danube to evaluate the importance of productivity in large rivers. Results indicate positive net production in the middle reach of the river and in impoundments. These sections are characterised by favourable conditions for algal growth. Reduction in flow, reduced concentrations of suspended solids and improved under-water light result in significant increase in plankton biomass. Maximum chlorophyll concentrations were below 20 mg m−3 in 2007 but concentrations up to 130 mg m−3 have been recorded in the past. Since nutrients are not limiting, as in most large rivers, net primary production is largely controlled by availability of photosynthetic active radiation under water, chlorophyll-a, water depth and discharge. Hourly carbon uptake rates of 3–130 mg C m−3 h−1 observed in the Danube are well within the range of 0–790 mg C m−3 h−1 for large rivers of the world. Autochthonous autotrophic production must be regarded as an important feature of large rivers supporting the RPM concept.