Ichthyocenosis of the Podolsky Brook spring section in the Hruby Jeseník mountains (Upper River Odra basin) within the context of the presence of fish predators

摘要

The study summarises results of the ichthyologic research of the Podolsky and St?íbrny brooks in Hruby Jeseník. The research was organised for the purpose of finding the actual situation in the fish settlements in the sections of interest and to make suggestions for their further management benefiting the original fish communities. The results have shown that there is the community of water organisms with naturally reproducing Cottus poecilopus and Salmo trutta in both partly adjusted water flows which have not been restocked by man since 1996. The facts found within the research suggest that the biologically correct way for the further development of fish populations in the Podolsky and St?íbrny brooks may be the maintenance of the existing natural conditions while no local adjustments of the flow beds along roads should be excluded. The research results have proved that the existing natural conditions and the very limited anthropogenic pressure put on the water biocenoses have been the decisive factors during the formation of the now existing fish population structures which can be assessed as good from the ecological point of view. Because of that we have recommended to the manager of the water flows neither interfering in the development of the current fish populations nor restocking any fishes. We consider the finding that the age structure and the high numbers of Salmo trutta and Cottus poecilopus have been, in the given situations, the indicators of their populations’ ability, even at the sympatric presence of Lutra lutra and Ciconia nigra, resistant against the predators’ pressure, as very important.