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Gradients of fish distribution in reservoirs
PRCHALOVÁ, Marie
Patterns of fish spatial distribution were studied in two Czech canyon-shaped reservoirs and in three Dutch basin-shaped reservoirs. Effects of environmental variables like habitat depth, slope, distance from the shore and distance from the dam were evaluated using multivariate statistics. Gillnet selectivity was also studied as fish were sampled using gillnets.
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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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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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Species composition along the vertical gradietn in canyon-shaped reservoirs
Prchalová, Marie ; Kubečka, Jan
During years 2004 and 2005, vertical gradients of fish distribution within two canyon-shaped Czech water supply reservoirs (Římov, Švihov) were examined by Nordic multimesh gillnets in both pelagic and benthic habitats. In the open water, most fish were found in the upper 5 m of depth. Below this depth nearly no fish occurred. The community was represented mainly by bleak. Towards deeper parts the portion of perch increased. In benthic areas, most fish were in the upper 3 m of depth. Abundance declined to 10 m and below this depth nearly no fish were present. Perch and roach dominated the littoral community. Ruffe preferred the deeper habitats. With respect to biomanipulative removal catches, it is sufficient to fish in the upper 5 m of the open water and in the upper 3 m in the littoral of the reservoir. For getting a rough but adequate assessment of fish community, it is satisfactory to sample the upper 5 m of the open water and the upper 10 m in the benthic part of the reservoir.
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Complex assessment of the fish assemblage of the Želivka reservoir, the biggest water supply reservoir in the ČR, in years 2004 and 2005
Prchalová, Marie ; Kubečka, Jan ; Jůza, Tomáš ; Říha, Milan ; Jarolím, Oldřich ; Tušer, Michal ; Peterka, Jiří ; Vašek, Mojmír
In the summer 2004 and 2005, the complex assessment of the fish assemblage of the Želivka reservoir (1432 ha) was carried out by gillnetting, adult and fry seining, adult and fry pelagic trawls and hydroacoustic sampling. Detailed picture of the fish assemblage was composed from every fishing gear from every depth strata of the open water as well as from the littoral zone. During two-years survey, 40.168 fish of 19 species and one hybrid were captured. The fish assemblage was dominated by cyprinid species in both years – bleak prevailed in the open water together with roach and bream; perch was abundant in the littoral zone. The assemblage of the Želivka reservoir was found to be in the stable cyprinid phase. The average abundance was 1.700 ind/ha and average biomass was 110 kg/ha. In the fish spatial distribution, the general gradients could be found – higher abundance and number of species in the tributary area and in the epilimnion and littoral.
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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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