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National Repository of Grey Literature 1 records found  Search took 0.00 seconds. 
Age and growth of the European grayling Thymallus thymallus (L.) originally from different localities - assessment based on the scale analysis
 CHYTRÝ, Martin
The main aim of this thesis is to evaluate and to compare the age and length growth of European grayling in selected watercourse in the South Bohemia (Blanice vodňanská, Volyňka, Teplá Vltava a Otava) and in Austria (the Traun River and the Salzach River), focusing on the watersources of the Teplá Vltava River and the Traun River. Possible rules adjustment of sport fishing can give reasons eventually to be done on the basis of results in order to protect and to strenghten natural populatin of grayling. 53 individuals (fish) were studied in total which were in observed localities fished from 2011 to 2015 using power generator or fishing rods. The determination of age and growth were based on analysis of scales of the biggest individuals. The method of Rosa Lee (1920) was used for back-calculation of length growth. The oldest fish, 8 years old, was found among graylings in the Teplá Vltava River. The oldest fish from studied group of fish in Austrian Traun River where graylings trophy are occured belonged to the age group 5+. Graylings from the Traun River came up to faster growth distinctly which is related to more optimal living conditions (water temperature, the amount of food) in the pariticular watersource. Furthermore graylings from observed watersources in the South Bohemian region already grow up to minimum fishing length (30 cm) at the age of 3 4 years old. They can participate in natural reproduction only once or twice a life. Increase of miminal fishing length is absolutely eligible and it is the reason for increasing number of natural spawning and strenghtening of indigenous population of grayling.
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