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Trout (Salmo trutta) catches in some districts in the Morava River Basin
Halačka, Karel
The study deals with differences in catch of salmonids (particularly the brown trout) by angling in various waters in Morava river drainage. Significant differences were found in average number of caught fish per hour (2 - 23), average length (17,1 - 21 cm) and in proportion of fish reaching the minimum size in a given water (0 - 5,8 %). The minimum size seems to be to high in many cases. Lowering of the minimum size can be recommended in order to preserve population numbers.
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Genetic diversity of grayling (Thymallus thymallus L.) populations in the Czech Republic inferred from microsatellite markers
Papoušek, Ivo ; Halačka, Karel ; Kohout, Jan ; Šlechta, Vlastimil ; Vetešník, Lukáš ; Mendel, Jan
The grayling is among the most valuable fish species in salmonid waters of the Czech Republic. Genetic diversity of twelve grayling populations from all three watersheds of the Czech Republic has been assessed by two multiplex analyses of ten microsatellite loci. Allele frequencies and tests of genotype frequencies for deviation from Hardy-Weinberg equilibrium were carried out. Relationships between respective populations were assessed by Factorial Correspondence Analysis and Principal Coordinate Analysis. Analysis of multilocus microsatellite genotypes from three watersheds of the Czech Republic has shown that significant variability is present in Czech grayling populations. However, this variability has no geographical structure; individuals from all three watersheds form no distinctive groups. It seems that the original genetic structure of Czech grayling populations has already been lost as they have been uniformized by artificial management.
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Population and genetic structure of trout (Salmo trutta) and grayling (Thymallus thymallus) as a basis for a successful fishery management
Halačka, Karel ; Papoušek, Ivo ; Kohout, Jan ; Vetešník, Lukáš ; Lusk, Stanislav ; Mendel, Jan ; Šlechta, Vlastimil
The aim of the study is to contribute to knowledge about population dynamics of our salmonids. The study concentrated particularly on the genetic diversity of Salmo trutta and Thymallus thymallus populations, and also on selected morphological characters. Genetic analyses of the mitochondrial DNA have shown an existence of an extreme uniformity of populations in all three sea-drainage areas. Due to anthropogenic interventions, structure local subpopulations adapted to given local subpopulations, resulting from the natural diversification spanning thousands of years, has been disrupted. All other individuals carried a uniform (Atlantic) haplotype. A comparison study dealing with structure and dynamics of epidermis in S. trutta, O. mykiss, S. fontinalis and T. thymallus has shown significant differences particularly in fraction of the secretory cells. Lower proportion of the secretory cells in T. thymallus could be related to its sensitivity to molds in the post-spawning period.
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Secundary trout zones and occurrence of grayling (Thymallus thymallus) in the territory of the Czech Republic
Halačka, Karel ; Lusk, Stanislav ; Vetešník, Lukáš
In this paper, the relationship between emergence of secondary trout zones below dams, and occurence of the grayling in the waters of the Czech Republic, is studied. The grayling was mentioned as a potentially perspective fish for our waters. This was confirmed by colossal growth of its catches in 1970s and 1980s. The space formed by creation of the secondary trout zones below series of dams, which were built at that time, was very significant for this growth. However, at the turn of the century, a breakpoint was observed, and the numbers of catches decreased to the level of the 1950s. It can be stated that these locaties appear very suitable for this species under specific conditions. However it is necessary to monitor the general dynamics of this biotope, in order to possibly establish an optimal regime fit for present organisms and therefore to form a stable equilibrium.
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