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Abstract: During its development into an important waterway the middle Elbe River underwent many anthropogenic influences, all of which strongly impacted the fish fauna assemblage. Both the river morphology and hydrology were affected by groyne field construction, with consequential changes of fish habitats along river banks. Variables in the ichthyofaunal composition of middle Elbe River groyne field areas and types were analyzed for their environmental influence based on data using a random point-abundance-sampling-strategy with an electrofishing device. Altogether 22 fish species and hybrids of cyprinids from eight families, mostly cyprinids and percids, were found. Habitat guilds were dominated by eurytopic fish species (40%), followed by the oligorheophilic guild (24%). The reproductive guilds were represented mainly by phyto-lithophils (36%) and phytophils (28%). The feeding guilds were dominated by benthivorous species (32%), followed by omnivorous and piscivorous species (each 24%). Most frequent were roach (Rutilus rutilus, 32.6%), perch (Perca fluviatilis, 29.7%), and ide (Leuciscus idus, 25.6%). The canonical correspondence analysis indicated that substrate, slope, and vegetation cover were the most important factors affecting the entire fish assemblage, including all age groups. The types of groyne fields were found to be mostly of minor importance with regard to differences in the ichthyofaunal structure. Fish assemblage at groyne heads and surrounding areas were compared to those in the siltation and static flow areas, whereby rheophilic fish species occurred most often at the groyne head and surrounding areas. The greatest temporal changes within the young-of-the-year (YOY) fish fauna were during the summer months June to August, where habitat shifts among the groyne field areas were a result of changes in YOY habitat requirements throughout the year. Hence, this study indicates that groyne fields are used as alternative habitats by a high number of different fish species and life stages and could therefore contribute to sustain a species-reach fish fauna in regulated lowland rivers. [Copyright &y& Elsevier]

Streams in North Rhine- Westphalia ( Germany) are frequently impacted by hydromorphological degradation leading to a loss of sensitive species and a reduction in diversity. These findings mean that the final objective of the European Water Framework Directive to achieve the good ecological status will be failed for a large number of streams. In a holistic approach, a new concept, considering the cost efficiency, has been developed to enhance habitats by morphological changes. This guide serves as a basis for stream restoration projects. The theoretical background is that near-natural sections influence adjacent sections of medium habitat quality positively by migration of type-specific sensitive organisms. The preconditions are a local taxa richness in the catchment area, the reduction of nutrients and organic matter, and the guarantee of free movement. This so-called 'spreading effect' can be measured upstream and downstream. The length of by these means valourized sections depends on the stream type and on the biological quality component. [ABSTRACT FROM AUTHOR]

Purpose: Although the water quality of the Rhine River in Europe has improved, contaminated sediments may still threaten fish populations. This is particularly likely in Upper Rhine oxbow lakes, which are connected to the main river channel only at one end, except for extreme flood events. The impact of such extreme flood events on the sediment toxicity has, however, not yet been investigated, although numerous oxbow lakes exist with varying degrees of connection to their main river channels. Materials and methods: We evaluated contaminants in sediments taken at ten sites along a 600-m transect in an oxbow lake in a nature reserve that receives sediment contamination only from the main river. Sediment was analysed for polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) as well as dioxins (PCDDs) and furans. The dioxin-like activity was measured using in vitro bioassays (7-ethoxyresorufin- O-deethylase (EROD) assay) on RTL-W1 cells. The distribution of sediment contaminants and effects in bioassay were compared within the oxbow lake and with other European water systems. Results and discussion: Chemical analysis of the 16 priority PAHs (1.12-2.16 mg kg), ∑PCDD/Fs (1.62-4.17 μg kg) and ∑PCB congeners 77, 81, 105, 118, 126, 156 and 169 (2.3-3.1 μg kg) showed low to moderate sediment contamination. However, all sediment samples showed dioxin-like activities with bio-TEQ values between 3.62 and 7.92 ng g in an EROD induction assay using RTL-W1 cells. These values were higher than those reported for other, larger river systems. Both contaminant levels and toxicity data clearly suggest a spatially homogenous exposure profile throughout the oxbow lake. This homogenous profile was caused most likely by extreme floods, which lead to a large input of river sediments and a mixture with remobilised lake sediments. Conclusions: This study illustrates the relevance of flood event-related contaminant input from the main river channel for connected oxbow lakes. This may impair their function as reproductive and developmental fish habitats. As the probability and temporal pattern of flood events in river systems may change due to climate change, this may also have direct consequences for the sediment contamination in connected oxbow lakes, and thus affect their ecological function for fish. [ABSTRACT FROM AUTHOR]

Abstract: The fish fauna in the northern part of the upper river Rhine close to the city of Karlsruhe (Germany) was analyzed by collecting fish from the cooling-water intake of a power plant (impingement method) between 1989 and 2001. With this method a total of 36 fish species were recorded. The results were compared between the years as well as with other studies on the fish fauna in this area. Particularly with regard to the physical structure of the river bed and banks, the pre-technical situation of the river Rhine has not been restored. However, the number of fish species has been augmented since the 1970s mainly due to improvements in the water quality and almost all autochthonous fish species are present again. Altogether only three introduced fish species (Sander lucioperca L., Lepomis gibbosus L., and Carassius auratus gibelio were found in this study. Among the long-distance migrating species three freshwater spawners (Lampetra fluviatilis, Petromyzon marinus and Salmo trutta trutta) were detected in addition to the catadromous eel. The eudominant fish species varied between years, i.e. the European eel, Anguilla anguilla, was the eudominant species 1989, whereas this species occurred in much lower numbers during the subsequent sampling campaigns. This clearly indicates that the high dominance of eels is mainly caused by stocking activities in the upper Rhine. In the following years roach, Rutilus rutilus was the eudominant fish species. Overall a positive development of the fish fauna in the upper Rhine over the last 15 years could be observed in terms of fish populations as well as in terms of species richness. [Copyright &y& Elsevier]