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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 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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Effect of catastrophic flooding on the composition of the fish stock of the Římov reservoir
Kubečka, Jan ; Prchalová, Marie ; Hladík, Milan ; Vašek, Mojmír ; Říha, Milan
In 2002, great flood occurred in the Římov reservoir. Fish stock of the reservoir was sampled before and after the flood by night beach seinings, pelagic and benthic gillnets, traps and electrofishing of spawning shoals of common bream. The fluctuations of most species (roach, bream and their hybrid, perch, ruffe, bleak, white bream, asp, pikeperch, eel, catfish) were random and can be attributed to interhabitat migrations rather to the effect of flooding. The share of certain species (carp, tench, goldfish, trout, dace, gudgeon) increased as they were flushed from ponds and fishing grounds in the catchment. Increased share of these species was detected in the spring 2003, while during August, the share of flooded fish decreased near to the usual level. The ‘climax’ cyprinid dominated fish stock proved itself to be very resistant to the extreme flood.
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