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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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