The habitat selection of European beaver (Castor fiber) was studied in Central Moravia (the Czech Republic). The Global Positioning System and Geographic Information System were used for mapping the habitat types and marks of beaver activity. Used and available habitats were compared by compositional analyses in two levels. Comparison of habitat use from home range compared to habitat availability in the study area gave Λ = 0.335 (P = 0.001), a simplified matrix ranked beaver habitat in the order: riverine willow scrub > willow- poplar forests of lowland rivers > hardwood forests > spruce plantations > meadows > reed and tall sedge beds > fields > river gravel banks > ruderal vegetation > oak-hornbeam forests > urbanized areas > ash-alder alluvial forests. Use of the habitat types based on the distribution of cut trees differed significantly from the habitat distribution within the home ranges (for habitat use quantified by number of cut trees Λ = 0.168, P = 0.001; for habitat use quantified by the time a beaver needs to cut trees Λ = 0.251, P = 0.003), the ranking matrix was: riverine willow scrub > willow-poplar forests of lowland rivers > ash-alder alluvial forests > hardwood forests of lowland rivers.
In Slovakia, Cobitis elongatoides (Bacescu et Mayer, 1969), Sabanejewia balcanica (Karaman, 1922), and Misgurnus fossilis (Linnaeus, 1758) are protected by national legislative, and localities of European importance have been delimited for these species within the Natura 2000 system. In Slovakia, the three species only occur in the Black Sea river system (the Danube and Tisza R. basin). Of them, C. elongatoides is the most widely distributed and most numerous both in its pure form and its hybrid, diploid-polyploid complexes (C. elongatoides x C. tanaitica). It occurs in proper streams and in natural as well as in artificial aquatic habitats, above all, in lowland regions. Comparing data on this species from 1955–1965, no major changes have been found. S. balcanica occurs chiefly in the middle reaches of rivers, first of all, in the Bodrog drainage area (the Laborec, Ondava, Topľa R.) in eastern Slovakia. In the western part of Slovakia (the Danube river system) the occurrence of this species is distinctly less frequent and insular. The distribution of the species has been markedly affected by water pollution, construction of dams and reservoirs, and river bed modifications. The occurrence of M. fossilis is almost exclusively limited to the lowland regions of eastern Slovakia and the Danube Lowland. In those regions, the amelioration measures taken during the second part of the 20th century caused the original natural wetlands to vanish – together with the occurrence of this species. However, M. fossilis found a secondary suitable environment in man-made hydro-amelioration channels, earth pits, and fishponds.
Juvenile 0+ fish communities in three adjacent stretches of two lowland rivers with different degrees of habitat modification were surveyed using electrofishing and evaluated as indicators of fish assemblage reproductive success and spatial distribution. Both rivers originally meandered through large flood plains, however both have been regulated and channelised, to a varying extent, during the last century. The first study stretch, the Czech stretch of the Morava River (69.4 – 92.8 r. km), was regulated by five weirs and completely separated from its floodplain. The second and third study stretches, the Slovak stretch of the Morava River (33.5 – 69.4 r. km) and the Dyje River (0 – 26.7 r. km), were not interrupted by weirs and their floodplain areas remain connected, though partially modified. The total number of 0+ fish species in all of the stretches recorded over three years was similar (22, 23 and 25 spp. resp.). The lowest value of the Shannon index of species diversity and the highest value of total relative density (CPUE) were documented in the Czech regulated-channelised stretch. Significant differences in species richness and relative density were documented among habitats.