The evaluation of resident fi sh communities is an important component of the ecological status assessment in aquatic habitats. Despite signifi cant water quality improvement in the Czech Republic in the last decade, several important pollution sources in the Elbe River basin remain. The aim of the study was to evaluate fish community in a chronically polluted part of the channelized lowland Elbe River and its potential indicative capability. The effluent from both industrial and municipal sewage treatment plant exhibited low pH, high conductivity and wide set of organic compounds (PAH, PCB, DDT etc.). Ecological characteristics of fi sh communities were obtained by boat electro fishing at selected sites in four inter-weir sections in July 2005 and 2006. Relatively high fish species richness (24 species) was observed in both seasons. Generalists (bleak, roach, chub) form the majority of the fish community in all four sections. There was no significant difference in fish species richness or density among study sections (river segments between weirs) even with a high level of measured organic compounds at the pollution inlet. Signifi cant differences in fish species richness and density were registered among individual sites within study sections. Sites downstream the weirs had signifi cantly higher species richness and density than the other two sites in the middle and upstream weirs. Fish community does not display any indicative remarks concerning water pollution, or in the case of mid-size river, sampling strategy was not effi cient to recognize it. Channelization and regulation of the study stretch of the Elbe River seems to be the most important determinant of fi sh community structure.
Juvenile 0+ fish communities in three adjacent stretches of two lowland rivers with different degrees of habitat modification were surveyed using electrofishing and evaluated as indicators of fish assemblage reproductive success and spatial distribution. Both rivers originally meandered through large flood plains, however both have been regulated and channelised, to a varying extent, during the last century. The first study stretch, the Czech stretch of the Morava River (69.4 – 92.8 r. km), was regulated by five weirs and completely separated from its floodplain. The second and third study stretches, the Slovak stretch of the Morava River (33.5 – 69.4 r. km) and the Dyje River (0 – 26.7 r. km), were not interrupted by weirs and their floodplain areas remain connected, though partially modified. The total number of 0+ fish species in all of the stretches recorded over three years was similar (22, 23 and 25 spp. resp.). The lowest value of the Shannon index of species diversity and the highest value of total relative density (CPUE) were documented in the Czech regulated-channelised stretch. Significant differences in species richness and relative density were documented among habitats.
Sledování přítomnosti cizorodých látek v rybách je ovlivněno řadou faktorů a jedním z nich je i výběr samotného monitorovaného, tzv. modelového druhu. Modelové druhy by měly splňovat určité podmínky a ne všechny druhy jsou pro použití k těmto účelům vhodné. Článek shrnuje výhody a nevýhody využití ryb pro monitoring cizorodých látek v říčních systémech a navrhuje nejvhodnější modelový druh - jelec tloušť (Squalius cephalus). and The monitoring of water pollutants in fish is influenced by many factors including the selection of model species (not all of the species are suitable for this purpose). This paper describes the advantages and disadvantages of different fish species for monitoring of water pollutants and suggests the most convenient model species – the European Chub (Squalius cephalus).