Recapture rate and growth of hatchery-reared brown trout (Salmo trutta v. fario, L.) in Blanice River and the effect of stocking on wild brown trout and grayling (Thymallus thymallus, L.)

Abstract

Summary Hatchery-reared adult brown trout, Salmo trutta v. fario L., [215–335 mm standard length (LS), n = 82] were individually tagged and released into three sections of the Blanice River in May 2007. Wild populations of brown trout and grayling, Thymallus thymallus, L., in these sections and three nonstocked control sections were also tagged. The recapture rate of hatchery-reared adult brown trout after 6 months (18%, n = 15) was comparable to that of wild adult brown trout in stocked (15%, n = 14) and control (14%, n = 11) sections. The recapture rates of wild brown trout and grayling after 6 months were higher in control sections than in stocked sections, but the differences were not significant. The movement of recaptured large juvenile wild brown trout from stocked sections was significantly higher (36%) than from control sections (9%). Wild brown trout growth and grayling growth were unaffected by stocking with adult hatchery-reared brown trout.