A novel sampling scheme, using a combination of electrofishing, visual exploration by scuba divers, two types of fyke nets and longlines, was tested in four reservoirs (including their inlets and outlets) to monitor a population of burbot Lota lota. This was supplemented by fry trawling and vertical hydro-acoustics, to detect L. lota larvae in two deep reservoirs that have had a long-term stocking programme. The majority of the L. lota detected were juveniles, captured by electrofishing in the littoral zones of the reservoirs and in running waters. Older individuals were rarely captured with longlines or fyke nets in deeper zones or structured habitats within the reservoirs. A combination of multiple sampling methods provided an assessment of the whole population. Population establishment could not be demonstrated as the age structure of the sampled fish corresponded with that of the stocked fish. Low post-stocking survival, migratory behaviour, interactions with other species and warmer water temperatures are considered the potential drivers for unsuccessful establishment of L. lota populations in these reservoirs.

Biology Centre of the Czech Academy of Sciences Institute of Hydrobiology Na Sádkách 7 370 05 České Budějovice Czech Republic

Faculty of Fisheries and Protection of Waters South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses Institute of Aquaculture and Protection of Waters University of South Bohemia in České Budějovice Husova tř 458 102 370 05 České Budějovice Czech Republic

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