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In many rheophilic fish species, young stages with low swimming capacities are confined to lateral habitats protected from the main current. Among these lateral habitats, we defined „dead zones” as small bays with shallow water and slow water current caused by physical structures (obstacles or curves of the bank), but without a clear frontier with the main channel. Nevertheless, a study using two...
Over the past centuries, rivers and streams across Europe and Northern America have increasingly been modified by damming and by other water regulation schemes. This situation is also becoming increasingly common throughout tropical regions. In the vast majority of cases, such schemes have been developed with little or no consideration to the ichthyofauna, and impacts on biodiversity and fisheries...
The present work has been aimed at the analysis of heavy metal (Cu, Zn, Mn, Fe, Pb, Cd) fate in selected food chains comprising molluscs, their potential food, fish feeding on molluscs and predatory fish as well as mollusc faeces, Chironomidae larvae and fish feeding on them. The results generally indicate a decrease of heavy metal concentrations in the successive trophic levels. Taking into account...
In this paper, we evaluate the effects of artificial reefs on fish assemblages in a hypereutrophic reservoir and in the lotic zone immediately below dam. Fish diversity was highest in the lotic zone relative to the reservoir. We also found an inverse relationship between diversity and distance from the river margin. Catches near the artificial reefs were more diverse than in control areas. A seasonal...
The 96 h LC50 values of copper for Carassius auratus and Xiphophorus helleri were 0.30 and 0.36 ppm. Sublethal concentrations of copper affected specific growth rate and reproductive performance in both species. Metal accumulation in muscle and gonad tissues was linearly increased with increase in sublethal levels of copper and exposure period. Young ones accumulated same or more amount of metal found...
A total of 272 specimens of R. amarus caught in Siahroud River at the southern Caspian Sea from March 2006 to February 2007 were examined for life history attributes. Length-at-age was different between sexes. The von Bertalnffy growth function fit to backcalculated size at age data were: Lt= 94.16 [1-e-0.31(t+0.321)] and Lt=92.33[1-e-0.32(t+0.488)] for males and females respectively. WLR was estimated...
The distribution of Lake Tana fish species was studied from January 2000 to December 2003. Samples were collected monthly using gill-nets of 60, 80, 100, 120 and 140 mm stretched mesh size. Labeobarbus spp., Oreochromis niloticus, Claris gariepinus and Varicorhinus beso are commercially important fish species and form 77%, 13%, 9% and 1% of the pooled experimental fish catch. There was significant...
In temperate zones, algae biomass may be efficiently controlled by Daphnia sp., which is the most significant grazer among filter-feeding zooplankton. Daphnia population dynamics depends mostly on the trophic state of the ecosystem, which determines both fish community structure and food quality and availability. Relatively invariable water inflow to a reservoir with small amplitudes supports balanced...
To improve our understanding of the hierarchy of human induced modifications of the natural environment, with particular regard to the controlling strength of the habitat or chemical impacts, it was found to be appropriate to employ indicators at a molecular level. This paper examines the potential use of the analysis of the RNA/DNA ratio for the evaluation of the ecological status of two rivers of...
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