Three species of the Eurasian family Cobitidae are distributed in Slovakia. In the present paper, we describe the coenological affinity of Cobitis elongatoides, Sabanejewia balcanica and Misgurnus fossilis in two distinct zoogeographical regions, Slovak Tisza and Danube basins and discuss possible differences of their biotop affinity and habitat preferences. The occurrence of S. balcanica is restricted to primary biotopes with harder substratum particles. Typical species assemblages for the rheophilic C. elongatoides are eurytopic and limnophilous species. C. elongatoides is mostly distributed in primary biotopes, such as rivers and channels. It also occurs in secondary biotopes (drainage canal or pit). M. fossilis is distributed mostly in the secondary biotopes, but it is also found in the primary biotopes. Both species prefer fine substratum, but spatial distribution of the two species is different. C. elongatoides prefers harder substratum of sandy particles mixed with mud or detritus and living vegetation, whereas M. fossilis prefers muddy substratum mixed with detritus and dead vegetation.
The following species of the genus Gobio occur in the Tisza River drainage area in Slovakia: G. Gobio, G. kesslerii, G. albipinnatus and G. uranoscopus. G. Gobio is the commonly distributed species. It occurs in streams of various sizes, attaining the largest numbers in streams populated by the barbel type fish communities. It occurs together with other Gobio spp., whith which it can produce hybrids. The present occurrence of G. Gobio has not changed basically from that in the past. G. albipinnatus occurs primarily in lowland streams, both in large rivers and canalised minor streams and channels. The distribution of this species in the Tisza River drainage area in Slovakia has not, appreciably changed from that in the previous period. According to earlier data, G. kesslerii was relatively abundant in the middle and upper reaches of a number of streams. At present the occurrence of this species has been confirmed in just a few localities so that its range has been markedly restricted. In some cases, however, the species may have been mistaken for G. albipinnatus. According to literary data, G. uranoscopus occurred in the past mainly in the upper reaches of rivers Torysa (the Hornád River drainage area), Topľa, Ondava, Laborec, and Uh (the Bodrog River drainage area). This species shows the most marked decrease in range, compared to that in the past. in recent times its presence has been confirmed only in a few localities. The devastating factors that have affected the distribution of the particular Gobio spp. include water pollution, stream and bed canalisation, decreased river bottom diversity, extraction of gravel materials, and hydro-energetic constructions (steps, weirs and dams). of the above gedgeon species, G. uranoscopus and G. kesslerii are protected by the national legislation in Slovakia. In accordance with the EU legislation (Council Directive 92/43/EEC), special protection regions (NATURA 2000) are being defined for G. uranoscopus, G. albipinnatus, and G. kesslerii.
The Amur sleeper, Perccottus glenii Dybowski, 1877, is indigenous in eastern Asia. During the second half of the 20th century, with the aid of man, it spread over the eastern part of Europe as well as in central Asia. In the course of 50 years of its dispersal in the western direction the species already reached the Vistula drainage area (the Baltic Sea basin) and the Danube drainage area (the Black Sea basin). In the latter basin, its occurrence was ascertained in the drainage area of the Tisza river in Hungary in 1997. In eastern Slovakia, the Amur sleeper was first recorded in 1998 in the Latorica drainage area. In the course of subsequent years it has become a common species in the streams in the basins of the Latorica, Bodrog and Tisza rivers. In shallow lentic waters densely grown with aquatic plants the species becomes a superdominant or even exclusive species in the local fish communities. It has no marketable value but presents a serious threat to the existence of native fish species with similar identical microhabitat requirements.
Seven populations (Oľšava/Hornád R., Oľšava/Topľa R., Ublianka R., Ondava R., Ipeľ R., Malý Dunaj R. and Vlára R.) of Balcan spined loach were subjected to phylogenetic analysis based on variability of the cytochrome b gene and mitochondrial specific marker. They were separated in to five groups but these groups were represented by specimens from different populations. Genetic distances among populations and among groups were quite low. Subsequently, analysis of relations among our groups and sublineages of Danubian-Balkanian complex of Sabanejewia was made. the first four groups were genetically close to sublineage III, while the fifth one to the sublineage IV. These findings agree with the conclusion about conspecificity of analysed Danubian-Dniester populations belonged to monotypic S. balcanica. Phylogenetic analysis showed that the most suitable populations for the restoration of this species in the Bečva River are populations dwelling the Ipeľ and Vlára rivers.
Genetic diversity of three pure populations of Cobitis elongatoides from hydrologically and geographically different drainage areas, the Lužnice River (48.49.60 N, 14.55.60 E, Labe River drainage area, North Sea basin), the Nová Říše reservoir (49.09.11 N, 15.32.464 E, Morava River drainage area, Black Sea basin), and the Ida River (48.32.284 N, 21.03.421 E, Tisza River drainage area, Black Sea basin) was evaluated by sequencing of mitochondrial cytochrome b gene. Species identification of unknown Cobitis samples from Vipava River drainage area in Slovenia was also performed based on cytochrome b sequence. All forms of the genus Cobitis are protected by national legislatives and, in accordance with the Council Directive No. 925/43/EEC, they enjoy protection in selected localities of European importance. In total, 11 haplotypes of Cobitis elongatoides were found in Czech and Slovak waters, manifesting low overall genetic diversity. Samples from Vipava River drainage area were identified as Cobitis bilineata.
Monitoring of the analysed populations of the endangered fish species Misgurnus fossilis was conducted using microsatellite analysis and sequencing of a part of the control region. Absolutely first microsatellite markers for weather loach were found. Six polymorphic microsatellite loci were prepared, five of which were tested. Number of alleles per a locus ranged from 3 to 5. All studied populations are differentiated one from another (FST= 0.205 - 0.367). All sampled populations contained unique alleles. Sequential analysis of the mitochondrial control region showed great haplotype similarity of the studied populations which come from one widely spread haplotype H_1, and thus suggested possible hypothesis of recent spreading from one source.
Sample of Gobio gobio from 30 localities in the Czech Republic and Slovak Republic were studied. Starch gel electrophoresis was used for evaluation of variability of allozyme patterns in 16 active protein systems comprising 26 loci. Products of 17 loci were considered to study the genetic structure of its populations. From this, genetic variability was found in ten loci, occurrence of rare alleles was detected in next four loci. Percentage of polymorphic loci ranged between 6 and 41%; mean occurrence of alleles was between 1.1 and 2.0 per locus; and mean heterozygosity was observed at 0.013 to 0.248. The genetic distances among populations were 0.002 to 0.175 (N e i 1972) and 0.063 to 0.385 (C a v a l l i - S f o r z a & E d w a r d s 1967). Differences in occurrence and frequencies of alleles in some loci among the sea basins were evident. Higher genetic variability identified in populations from the Danube river system (Black See basin) is probably connected with the fact that this basin served as a refuge for ichthyofauna during glaciations.
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.