The growth, and dispersal of stocked European grayling Thymallus thymallus, reared in a hatchery (fed dry food pellets) or in a pond (fed natural food), compared with their wild conspecifics was assessed from the recapture of individually tagged fish 168 days after their release into the Blanice River, Czech Republic. Recapture rates and site fidelity were higher for wild T. thymallus than for artificially reared fish. Specific growth rate and upstream or downstream dispersal did not significantly differ between any of the groups of fish. An influence of rearing conditions (pond v. hatchery) on the overall performance of stocked fish was not demonstrated. Initially, lower condition factors of reared T. thymallus were equal to wild fish after recapture, suggesting adaptation of artificially reared fish that remained in the sections studied.

University of South Bohemia Ceské Budejovice Faculty of Fisheries and Protection of Waters Research Institute of Fish Culture and Hydrobiology Zátisí 728 2 Vodnany Czech Republic

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Is it possible to contribute to the recovery of European grayling (Thymallus thymallus, Salmonidae) populations by stocking cultured brood fish in the pre-spawning period?