We examined the abundance and meso-habitat use of gobiid species during both day and night along 43 stretches (500-m long) of the littoral zone at five locations of the Middle Danube, Hungary, in spring and in summer 2004. Electrofishing catch per unit effort sampling revealed significantly higher relative densities at night than during the day. Gobiids occupied all the available habitats encountered during sampling. Habitat-abundance relationships from night-time samples revealed that the two most abundant species, round goby Neogobius melanostomus and bighead goby Neogobius kessleri, were found in highest relative density along gravel beach and artificial rip-rap habitats; these species were in relatively low density in sandy areas. Monkey goby Neogobius fluviatilis was more abundant in natural shorelines than in rip-rap habitats and dispersed more consistently between sandy and gravel beaches. Tubenose goby Proterorhinus marmoratus demonstrated great plasticity in meso-habitat use. In conclusion, Ponto-Caspian gobies occurred rather consistently along the Hungarian section of the Danube, occupying all available habitats examined. Abundance-habitat relations suggest plasticity in meso-habitat use but partial segregation between species. Further studies are required at multiple spatial scales to assess how micro-and meso-habitat use varies with fluctuating population densities.

We studied day-night patterns in fish diversity in natural, gravel-sand stretches and boulder covered rip-rap habitats in the littoral zone of the River Danube. Sample-based rarefaction indicated marked differences in species richness between day and night, and smaller differences between habitats for both day and night. Whereas, individual-based rarefaction indicated no such substantial differences in species richness. However, distinct fish assemblages were found based on relative abundance data, and species of great conservation concern tended to link to natural habitats. The diversity of biological traits/attributes were generally higher in rip-rap habitats. The differences in fish assemblage characteristics between habitats revealed the importance of gravel-sand habitats in maintaining natural assemblages and that riprap sections increase compositional beta diversity at the mesohabitat scale.

23The organization of fish assemblages in offshore, deep channel habitats is poorly known in 24 very large rivers compared with shoreline, littoral areas. We report on the parameters and 25 testing of an electrified benthic frame trawl (EBFT), developed for monitoring the distribution Zingel streber in the river, which proved to be extremely rare in SE catches. The EBFT 35 caught larger/older individuals of many species than SE, and indicated diverse size/age 36 structure for many species offshore. Our survey revealed that offshore areas are intensively 37 used by a variety of species, which occur relatively evenly, but with variable abundance in the 38 Danube River. We suggest that even a relatively small (i.e. 2 m wide 1 m high) EBFT can be

The Nearctic leafminer of black walnut Coptodisca juglandiella (Chambers, 1874) was found in Hungary and reported as new for Europe. Larvae were found in leafmines on black walnut (Juglans nigra (L.)), white walnut (J. cinerea (L.)) and Arizona walnut (J. major (Torr.)); the latter two Juglans species are new host plant records for C. juglandiella. Mines of Coptodisca lucifluella (Clemens, 1860), another Nearctic invader, were found on leaves of bitternut hickory (Carya cordiformis (Wangenh.) K.Koch) and Caucasian wingnut (Pterocarya fraxinifolia (Lam). Spach.) (a new hostplant record), in addition to common walnut (Juglans regia L.). Interestingly, C. lucifluella is thought to have performed a host plant shift after its introduction into Europe, whereas C. juglandiella apparently did not. Coptodisca juglandiella has three generations in Hungary. The autumn generations of both species produced many more mines than the spring generations. One hymenopteran parasitoid specimen was reared from C. juglandiella. Larvae, mines and adults of C. juglandiella and C. juglandiella can be easily distinguished, differences are presented and illustrated. The genitalia of C. juglandiella are described for the first time.

Halting biodiversity loss is a critical aim for the forthcoming decades, but is hindered by the gap between research and practice. Bridging this gap is a significant challenge in the countries of Central and Eastern Europe, where, compared to Western European countries, biodiversity is higher but the research budget is lower. Approaches to address bridging this gap include participatory research prioritizing exercises. These demand-driven collaborative ranking processes have proven to be a useful tool in providing a research agenda derived from a review of critical challenges based on stakeholder engagement. However, for research agendas to be effectively realized, they are best developed and implemented at the operative level of research financing and implementation. This paper shows the process and the outcome of an exercise conducted in Hungary aiming to compile the most important conservation research questions at the country-level and outlines a set of further measures and tools required for dissemination and advocacy for the research agenda. During the process 792 research questions were collated from conservation practitioners and natural resource managers based on interviews and via an online questionnaire; the final 50 most important questions were identified by practitioners and policy makers during an expert workshop. Questions are embedded in global and EU biodiversity targets and imply a pragmatic approach with the aim of identifying research that supports policy-and decision-making regarding habitat management, landuse and regional development, while also focussing on conflicting issues. The outcome of the process includes the potential for lobbying, therefore post-publication activities and dissemination strategies are outlined as an integrated part of the exercise.

Hydromorphological features of rivers, such as flow depth, flow velocity, and the composition of bed material play a crucial role in the habitat selection of fish. Although these basic hydromorphological parameters can be determined with high spatial and temporal resolution using state‐of‐the‐art investigation methods, only few studies deal with the connection of habitat parameters and abundance of fishes (i.e., habitat modelling) in large rivers. The aim of this study is to fill this gap by introducing the so‐called habitat maps connecting the results of 3D hydrodynamic simulations and results of offshore fish ecological surveys. The steps of habitat modelling are introduced through the case study of the Danube River focusing on evaluating the habitat use and suitability of two fish species representative to this section of the river (i.e., the round goby Neogobius melanostomus and the Danube streber Zingel streber). A novel method for mapping the bed material composition, playing a crucial role in the habitat assessment, is also presented along the numerical modelling.

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In Europe 37% of freshwater fish are threatened. However, conservation activity is less widespread for fish compared to other vertebrate groups. The Vulnerable European mudminnow Umbra krameri is a marshland fish endemic to the Carpathian Basin. Its range and population have declined significantly since the 1990s. The main threats to the species are habitat loss and the invasive Chinese sleeper Perccottus glenii. During 2008–2012 a species conservation programme was established to rescue broodstocks from threatened populations, breed them under controlled conditions, translocate both rescued fish and their laboratory-reared offspring to surrogate habitats, and finally reintroduce offspring to their original habitats. Broodstocks from three threatened habitats were bred in the laboratory and produced offspring appropriate for stocking. Six artificial ponds were created in the pilot study area according to the environmental needs of the species, four of which proved to be suitable surrogate habitats in which translocated fish survived and reproduced successfully. Populations in the original habitats were supplemented with fish from laboratory breeding and from the natural recruitment of surrogate habitats, with special care of the corresponding broodstocks. Future challenges include improving our knowledge about the ecological processes in which the European mudminnow participates, identifying the most threatened populations, habitats suitable for restoration and potential areas for creation of surrogate habitats, and enhancing induced propagation methodology.