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Non-indigenous invasive topmouth gudgeon (Pseudorasbora parva) was introduced to Europe in 1960s and it has passed an ongoing invasion into many European countries. It forms numerous populations particularly in pond aquaculture systems and small stagnant water bodies. The study was carried out on a 0.3 ha pond inhabited solely by the population of topmouth gudgeon. Monthly samplings of environmental variables, zooplankton, macrozoobenthos and fish were performed in 2016–2017. Topmouth gudgeon recruitment correlated with decrease of oxygen concentration and transparency in summer months, apparently due to topmouth gudgeon predation on the cladocerans. The macrozoobenthos community was dominated by large chironomid larvae (Chironomus plumosus), whose density and biomass were not affected by the topmouth gudgeon population. The habitat preferences varied within the population. The 0 + age cohort were abundant in rocky rip-rap, muddy and macrophyte habitats with low abundance in free water zone. In contrast, the 1 + and older fish significantly preferred the rocky rip-rap habitat and free water zone over muddy and macrophyte substrates. In spring, the rocky rip-rap was occupied mainly by males, while later in June and July, females predominated in this habitat. The study also documented disapperance of topmouth gudgeon population due to sudden spate flash-flood. [ABSTRACT FROM AUTHOR]

Efforts to positively influence ecological processes and water quality by manipulating the fish community (biomanipulation) are of particular importance in drinking water reservoirs. One of the principle measures employed is to increase the abundance of predatory fish species as a means of reducing planktonophagous and benthophagous cyprinids. However, there is little information available on the effectiveness of different predatory fish in biomanipulation exercises. We examined the diet of the five dominant predatory species (pike Esox lucius, zander Sander lucioperca, asp Leuciscus aspius, European catfish Silurus glanis, and perch Perca fluviatilis) in five representative reservoirs in the Morava River drainage basin (Czech Republic). Fish prey made up 75% of total food intake, with undesirable small cyprinids dominant by biomass (40%). European catfish and asp were not taken as prey and showed no sign of cannibalism. On the other hand, predation on conspecific predatory species (including cannibalism) was relatively high in perch, pike and zander, thereby reducing their net benefit overall. This little-considered aspect of predatory feeding needs to be taken into consideration in future biomanipulation stocking strategies. [ABSTRACT FROM AUTHOR]

One of the main assumed impacts of invasive gobies is predation on benthic macroinvertebrates. Despite numerous dietary studies, however, quantitative evaluations of impact in European river systems are scarce. Here, we investigate the impact of tubenose ( Proterorhinus semilunaris, Heckel 1837) and round ( Neogobius melanostomus, Pallas 1814) gobies on macroinvertebrates in a lowland river (River Dyje, Czech Republic) by allowing and preventing gobiid access to rip-rap substrate naturally colonised by invertebrates at two sites (Site 1-tubenose goby only, Site 2-tubenose and round gobies). Gobies had a negative impact on invertebrates at both sites, with overall invertebrate density reduced by 15% (ca. 17.9 g m per year) at Site 1 and 36% (ca. 23.6 g m per year) at Site 2. Both species showed increased impact in summer and ingested larger invertebrates preferentially, resulting in an overall reduction in invertebrate body size. Tubenose gobies had a significant impact on Annelida, Gastropoda, Crustacea and Ephemeroptera nymphs, while tubenose and round goby together impacted Annelida, Bivalvia ( Dreissena), Gastropoda, Crustacea, Ephemeroptera nymphs, Odonata nymphs and Chironomidae larvae. Our results confirm that round and tubenose gobies can have a significant negative impact on aquatic invertebrate density and community composition. [ABSTRACT FROM AUTHOR]

The paper is focused on the issue of metals migration within the forest environment affected by deep mining of metals and the possibility how to immobilize them using an environment-friendly method. First, the paper presents the information about metal content in the tree leaves in alluvial recipients polluted by metals from uranium deep mining at Dolni Rožinka, the Czech Republic. X-ray fluorescence analysis of dried leaves results showed the increased content of Cu, Fe, Mn, Ni, Rb, Sr, Zn and U; it corresponds to the most seriously polluted areas in the world comparing with the scientific literature. However, statistically, we did not succeed to demonstrate in none of areas of interest the element heterogeneity between the upper, middle and lower streams segments. Element habitat homogeneity can be caused by current stand species composition where Picea abies L. dominates and this fact results in the negative impact on the soil pH since it is a primary factor of metals immobilization in the ecosystem and their transformation into toxic variations. Within the area of interest, there is demonstrated positive effect of reconstruction of forest stands, which are close to the dominating deciduous trees, especially Fagus silvatica L. This management change in the selected interested forest stands can result in Ca supply of up to 39 kg.ha-1 from strictly natural sources, which might be a perspective alternative to liming. [ABSTRACT FROM AUTHOR]

Oxbow lakes are specialised standing water bodies that often support unique macrophyte and animal communities. Between 2015 and 2016, we assessed the diet composition of adult rudd (Scardinius erythrophthalmus) in one such macrophyte-rich lake. Over 2016, we also undertook a series of feeding behaviour tests under artificial conditions, the aim being to assess whether adult rudd represent a threat to the endangered sharp-leaved pondweed (Potamogeton acutifolius). In total, we examined 100 digestive tracts of rudd feeding under natural conditions and 100 from rudd feeding under artificial conditions. Our results show that i) P. acutifolius is deliberately consumed by rudd, and ii) pondweeds, periphyton and invertebrates were the dominant dietary components in the diet. A reluctance to consume cleaned P. acutifolius suggests a link with periphyton and invertebrate consumption. While rudd clearly consume P. acutifolius, we found no evidence of any negative impact on either pondweed development or on the macrophyte community as a whole. [ABSTRACT FROM AUTHOR]

While fish communities have been studied in Czech reservoirs for decades, monitoring has increased since implementation of the EU Water Framework Directive (2000 / 60 / EC). Despite this, many smaller drinking water reservoirs have yet to be surveyed. Between May and July 2016, we undertook a pilot-study examining the fish communities of five Moravian reservoirs (Ludkovice, Bojkovice, Hubenov, Nová Říše and Landštejn). Fish were sampled using boat electrofishing along the littoral zone and Nordic gill nets in the pelagic zone. Both methods were evaluated separately and combined as CPUE and relative abundance and biomass ( %). Nineteen fish species and one hybrid were recorded, with roach Rutilus rutilus dominating overall by abundance, but carp Cyprinus carpio, pike Esox lucius and wels Silurus glanis dominating by biomass in electrofishing samples. Predatory species represented up to 60 % of biomass in the combined sample, with an F / C index ranging from 0.5 - 3, implying a high abundance of predators. Electrofishing tended to underestimate the abundance of bleak and ruffe, while gill nets underestimated the biomass of predatory species. In some reservoirs, the abundance of pike and wels was high (though it is difficult to say if these fish were stocked or the result of natural reproduction). In others (e.g. Landštejn), zander Sander lucioperca were not registered by either sampling method, despite intensive stocking. Overall, gill netting alone appears inadequate for gaining a true picture of the fish community in reservoirs and we suggest a combination of electrofishing and gill netting in future. [ABSTRACT FROM AUTHOR]