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The effect of floods on the ichthyofauna of Štěpánovský stream
Čech, Martin ; Čech, P.
The effect of floods on the ichthyofauna of Štěpánovský stream (left-hand affluent of Sázava River, aver. summer flow rate 0.2 m3s-1) was studied using diet analysis of kingfisher A. atthis preying exclusively on local fish community. The first local flood event (2 August 2001; flow rate 100 m3s-1) caused drastic shift in the ichthyofauna composition from original fish community dominated by brown trout S. trutta, brook trout S. fontinalis and bullhead C. gobio to fish community dominated by bleak A. alburnus, roach R. rutilus, chub L. cephalus and gudgeon G. gobio. The second flood event (all Czech Republic floods in August 2002; flow rate 4 m3s-1) was surprisingly much less destructive to fish fauna. Consequently, the stream played also the role of refuge for many new fish species including juveniles of nase C. nasus, vimba bream V. vimba, barbel B. barbus, asp A. aspius and sunbleak L. delineatus, from highly flooded Sázava River.
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The natural fish reproduction of lowland stretches of Morava and Dyje rivers
Valová, Z. ; Jurajda, Pavel
Lowland rivers decreased their habitat diversity and get an uniform character due to their regulation and channelisation. This modifications affected the natural fish reproduction. The efficiency of natural fish reproduction was studied using Point Abundance Sampling strategy by electrofishing in three differently modified stretches of two adjacent lowland rivers in the late summer of 1999-2003.
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Comparison of efficiency of different electrofishing techniques for juvenile fish estimates on river beach
Janáč, Michal ; Jurajda, Pavel
The efficiency of three PAS electrofishing techniques (direct electrofishing, throwing of anode and remote electrofishing) for 0+ juvenile fish estimates was tested on gravel beaches of the Morava River. All three techniques yielded significantly different assemblage structure (in terms of relative abundances of most abundant species). Both direct electrofishing and throwing of anode disturbed fish what lowered their efficiency on these shallow habitats (30% efficiency in comparison with remote electrofishing). Remote electrofishing was the most effective technique; moreover it yielded significantly more species per locality than other two techniques. Higher time consumption, caused by higher number of fish caught, may be its only constrain in common monitoring, however it is negligible in comparison with its benefits.
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The influence of ploidy on the complete blood count in silver crucian carp
Vetešník, Lukáš ; Halačka, Karel ; Lusková, Věra ; Lusk, Stanislav
In the sample of 27 specimens of silver crucian carp (Carassius auratus) of different ploidy (5 diploids, 21 triploids and 1 tetraploid), the red component of complete blood count was found. Using the analysis of variance test, highly significantly lower erythrocyte count, insignificantly lower haemoglobin count and haematocrit value were proved. The mean corpuscular volume was increasing significantly with the ploidy increased, and mean corpuscular haemoglobin was increasing highly significantly with the ploidy increased.The tetraploid specimen indicated similar trend depending on the higher ploidy level.
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Development of brown trout (Salmo trutta) after hatching: comparative analysis of parents influence, originating from the natural and artificial living environment
Prokeš, Miroslav ; Randák, T. ; Peňáz, Milan ; Baruš, Vlastimil ; Žlábek, V.
Early development of brown trout (Salmo trutta L.) in the period after hatching was analysed. Three different series (A, B, C) of eleuterembryos, larvae and juveniles were compared by means of selected morphometry parameters (total length, fork length, standard length, head length, body depth, yolk sac length, height and depth, body height, mouth width and mouth diameter). Development of fry originating from parents from natural environment (line A) and from artificial environment (line B) was standard without significant differences. Growth rate of fry in line C (female from artificial environment and male from natural conditions) was slower in the period with exogenous nutrition. Combination C showed from a stand point of ours results as a little acceptable for production of fish stock.
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Early development of ide (Leuciscus idus): species determining parameters
Prokeš, Miroslav ; Peňáz, Milan ; Baruš, Vlastimil ; Hamáčková, J. ; Lepič, P. ; Kozák, P. ; Policar, T.
Main species determinant characters of dace (Leuciscus idus) in the early ontogeny were described and compared with analogical parameters referred in literature with chub (Leuciscus cephalus) and dace (Leuciscus leuciscus). Dealt about of morphological and morphometrical characteristics of eggs, free embryos, larvae and juvenile individuals (egg diameters, embryo lengths at hatching, larvae lengths at the start of exogenous nutrition, juvenile individuals lengths at the time of scale formation, number of body and caudal segments, number of fin rays, number of scales, mouth and fin position, caudal fin laps depth, fin coloration, pigmentation and next characters). The ide is morphologically very similar with the chub and dace. Species determination during early ontogeny is difficult.
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