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The River Bečva occurs at the confluence of Rožnovská Bečva and Vsetínská Bečva rivers in Valašské Meziříčí. Fishes inhabiting River Bečva present a typical fish composition characteristic for barbel zone. Ichthyological research of its both sources done in 1997 and 1999 has confirmed that the sources are the flows in which the barbel zone communities above the confluence progressively transform into grayling and trout inhabited waters having the high ratio of dominating brown trout, common minnow and, in the highest sections, europian bullhead, alpine bullhead respectively. The low transformation sections having barbel zone species present variable species, abundance and high ichthyocenosis biomass. There are 9–12 species in the River Vsetínská Bečva. The estimated biomass is 200–500 kg.ha-1 and the density 3–6 thousand units per hectare. The River Rožnovská Bečva presents 9–10 species, the estimated biomass 250–610 kg.ha-1 and the density 5.5–18.2 thousand units per hectare. The quantitative parameters of fish populations in the upper source sections are lower showing 1–5 species, the estimated biomass is usually below 100 kg.ha-1, exceptionally even 200 kg and the density ranging from 1.1 to 3.2 thousand units per hectare. Angling activities take place in both sources. There are brown trout and grayling introduced and even the not original rainbow trout in limited numbers. Source tributaries, which are inhabited by alpine bulhead populations, are used for the breeding of brown trout. [ABSTRACT FROM AUTHOR]

This study identifies of populations of the genus Cobitis from the Slovakian Tisza drainage area, using karyotype, enzyme electrophoresis and flow cytometry. Pure diploid populations of Cobitis elongatoides were found in drainage basins of the Hornád, Slaná and Bodva rivers (5 populations). Species identifity was proven by analysis of genome and allelic composition. A large number of males was in these populations (42.5-60%). The drainage basin of the Bodrog river (3 populations), harbored so-called hybrid diploid-polyploid complexes with basic composition C. 2 elongatoides x 1 tanaitica. If diploid specimens were found, they belonged to C. elongatoides. Apart from triploids, diploids were rarely found in the Ondava and Latorica rivers. In the Bodrog River, tetraploids (C. 3 elongatoides x 1 tanaitica were seldom found beside triploid and diploid individuals. The percentage of males in hybrid complexes was very low (up to 16.2 %).

Samples from 37 populations of spined loach (Cobitis) pure species and their hybrid complexes - were examined using gel electrophoresis for the interspecific variability in 27 protein coding loci. Up to now, species-specific and species distinguishing variants in different protein/enzyme loci were found in Cobitis bilineata, C. elongata, C. elongatoides, C. cf. fahirae, C. strumicae, C. taenia, C. tanaitica, and C. turcica. The species-specific differences in the occurrence of such variants were found in 11 loci for these Cobitis species. This allowed us both identification of species and recognition of interspecific hybrids in many complexes. Besides this we were able in many cases of polyploid hybrids to estimate their genomic composition.