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 random amplified polymorphic DNA (RAPD) method was applied to eight Gobio gobio populations living in the rivers of the Czech Republic and Slovakia. The application of seven RAPD primers yielded eight fingerprint characteristics for the populations examined. Forty diagnostic markers have been identified, which can reliably identify the populations under study. Intrapopulation diversity varied between 0.26 and 0.38. A phenogram documented the close agreement of the particular populations with the geographic pertinence of their localities to the different sea basins.
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.
The occurrence of common gudgeon in the River Morača drainage of southern Montenegro was investigated. Low numbers of specimens were recorded in four out of five localities investigated on the Zeta River and at a single locality on the lower part of the River Morača. Allozyme analysis revealed that the specimens examined belong to the species Gobio gobio (Linnaeus, 1758). The lower number of lateral line scales in common gudgeon from the Ohrid-Drim-Skadar system, as compared with other European populations, probably indicates clinal variability. The results also demonstrate that the subspecies Gobio gobio ohridanus Karaman, 1924 is not a valid taxon.