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Monitorování rybích obsádek údolních nádrží v České republice – výsledky prvního roku sledování
Peterka, Jiří ; Čech, Martin ; Frouzová, Jaroslava ; Draštík, Vladislav ; Vašek, Mojmír ; Prchalová, Marie ; Matěna, Josef ; Kubečka, Jan ; Jůza, Tomáš ; Kratochvíl, Michal
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How shall we study the fish stock of our large water reservoirs?
Kubečka, Jan ; Matěna, Josef ; Čech, Martin ; Draštík, Vladislav ; Frouzová, Jaroslava ; Hohausová, Eva ; Jarolím, Oldřich ; Jůza, Tomáš ; Kratochvíl, Michal ; Muška, Milan ; Peterka, Jiří ; Prchalová, Marie ; Říha, Milan ; Tušer, Michal ; Vašek, Mojmír
Quantitative fish stock assessment recently advanced significantly in the Czech Republic. Sampling of open water was facilitated by application of scientific echosounders, trawls, Nordic multimesh gillnets, purse seines and booming electoshockers. Simplified combination of the above methods was recommended for the monitoring of larger stagnant water the Water Framework Directive of EU. Combination of all above approaches with more classic ones (beach seining, benthic gillnets) is being used for „complex fish stock assessment“ providing the assessment of abundance, biomass, species and age composition of all important species in all important habitats of the reservoirs. Further improvements of results is likely to be achieved by the application of multibeam acoustic cameras and by mitigation of the problems connected with quantitative trawling of large fish
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Fish stock of the Orlík Reservoir after first years of operation of Temelín Nuclear power plant
Kubečka, Jan ; Čech, Martin ; Říha, Milan ; Jůza, Tomáš ; Frouzová, Jaroslava ; Draštík, Vladislav ; Hladík, Milan ; Kratochvíl, Michal ; Prchalová, Marie ; Tušer, Michal ; Vašek, Mojmír
The fish stock of the Orlik reservoir, Czech Republic was surveyed by shore seining and scientific echosounder (Simrad EY 500). Reservoir was dominated by cyprinids (roach, bream) with considerable share of predatory fish and perch. Inshore biomass an abundance was 302 kg/ha and 3920 inds/ha respectively. Populations show sustainable recruitment without variation of year class strength. The open water biomass estimated by hydroacoustics was 145.5 kg/ha. Assuming hydrological conditions of light flood in June 2004 it was not possible to trace any changes of the fish stock of the reservoir connected with the operation of the Temelin nuclear power station.
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Sampling of the offshore fry fish communities of reservoirs by trawls
Jůza, Tomáš ; Kubečka, Jan ; Čech, Martin ; Draštík, Vladislav ; Jarolím, Oldřich ; Peterka, Jiří ; Vašek, Mojmír
The offshore area of six Czech reservoirs was sampled by pelagic fry trawl in late summer in 2003-2005. In Římov, Želivka, Vrané and Slapy reservoirs cyprinids dominated in offshore area. The main species here were roach, bream and bleak. In Lipno and Nýrsko reservoirs percids dominated in offshore area (Lipno-pikeperch, Nýrsko-perch). Trawling in offshore areas revealed that almost all 0+ fish were caught in the surface stratum (0-3m depth). In reservoirs where percids and cyprinids occured together, cyprinids dominated in 0-3m depth while percids usually prevailed in catches of 0+ fish from 3-6m depth. In ordinary canyon-shaped reservoir like Římov and Želivka the 0+ fish abundance decreased from the upstream end toward the dam, so the biggest abundance was in tributary area. In cascade reservoirs like Slapy and Vrané, the offshore area in tributary is almost without fish. The peak of abundance is more downstream and from this place, the trend is similiar to non-cascade reservoirs.
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Fish diversity and spatial distribution of YOY fish in Vlatava cascade reservoirs
Draštík, Vladislav ; Kubečka, Jan ; Jůza, Tomáš ; Jarolím, Oldřich ; Hladík, Milan ; Kratochvíl, Michal ; Prchalová, Marie ; Říha, Milan ; Tušer, Michal
Fish communities of YOY were studied in four cascade reservoir by beach fry-seining and fry trawling. Highest fish fry density was found in Slapy and Vrané reservoir. Lowest density was found in Kamýk and Štěchovice reservoir, two small reservoirs with shortest retention time, lowest oxygen concentration and temperature. Pelagic fish fry assemblages had much lower density than littoral assemblages and follow general fish longitudinal gradient. Littoral assemblages were more difficult to interpret due to more factors which can play important role in fish fry spatial distribution (such as bottom substrate and slope, complexity of shoreline, availability of water vegetation). Cyprinid species (bleak (.i.Alburnus alburnus./i.), roach (.i.Rutilus rutilus./i.), bream (.i.Abramis brama./i.)) prevailed in most reservoirs, only in Kamýk reservoir percid species (perch (.i.Perca fluvitilis./i.), ruffe (.i.Gymnocephalus cernua./i.)) prevailed.
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Giant traps for fishing in the inflow-zone of the Římov reservoir
Hladík, Milan ; Kubečka, Jan ; Pokorný, P. ; Čech, Martin ; Draštík, Vladislav ; Kratochvíl, Michal ; Peterka, Jiří ; Prchalová, Marie ; Vašek, Mojmír
The fish stock of the inflow-zone of the Římov Reservoir was studied by using two special constructed big traps. One trap was sampling the fish migrating from the reservoir to the Malse River, the other was sampling downstream migrants. The most intensive fish movement was recorded during spring spawning season. Proportionally to the fish stock of the reservoir, the tributary zone was used mainly by the bleak, .i.Alburnus alburnus./i., Asp, .i.Aspius aspius./i. and roach .i.Rutilus rutilus./i.. Smaller affinity to tributary spawning was found for the bream .i.Abramis brama./i. and perch, .i.Perca fluviatilis./i. (5 to 10 % of reservoir fish spawning in the tributary). Over 6000 kg of migrating fish were captured in the tributary area during spring periods of three years. Consequences of the application of tributary traps for fish exploitation and management are being discussed.
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