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The study summarises results of the ichthyologic research of the Podolský and Stříbrný brooks in Hrubý Jeseník. The research was organised for the purpose of finding the actual situation in the fish settlements in the sections of interest and to make suggestions for their further management benefiting the original fish communities.

There has been the assessment of current occurrence and situation of non-native fish species in two hydrological regions – the Upper Odra and Morava river basins. The river basin of Upper Odra is situated in the area of River Odra springs featuring mostly minor streams which are not currently accessible for the migration of fishes from the lower river parts and from the Baltic Sea because of the existence of tens of migration barriers in the area of Poland. There has been actually proved the occurrence of eight non-native fish species the presence of which is, with the exclusions of Carassius gibelioand Pseudorasbora parva,the result of the planned introduction related to the fish management activities. The River Morava basin consists of two parts – the system of the River Morava itself and the entire River Dyje basin. Currently, there are 16 non-native fish species. Apart from the eight species existing also in the Odra river basin, there are also eight other species the existence of which relates to the migration accessibility from the confluence of these two rivers for fishes from the River Danube through the lower part of the River Morava. The species Lepomis gibbosus, Neogobius melanostomusand Proterorhinchus semilunariswere the last ones which have arrived there by themselves. Coregonus maraenaand Coregonus peledare bred in fishponds.

The assessment of changes in the population spread of individual ichthyofauna species (lampreys and fishes) as well as the identification of unfavourable impacts is the necessary prerequisite for the correct selection of corrective measures. The river network in the Czech Republic belongs to the three sea-drainage areas (North Sea, Baltic Sea, and Black Sea). The species composition of the original ichthyofauna and the extent of the threat to some species differs in the individual sea-drainage areas. The original ichthyofauna in the Czech Republic consists of 4 lamprey species and 55 fish species. Out of this, only one lamprey species and 31 fish species originate in all three sea-drainage areas. There are 37 fish species considered as the original ones in the North Sea drainage area, there of 4 species are EX, 1 species EW, and 11 species (29.7%) are threatened. In the Baltic Sea drainage area, there are 4 species EX, 1 species EW, and 8 species (22.8%) threatened out of the total 35 assessed species. Out of 49 species in the Black Sea drainage area, there are 4 species EX and 23 species (46.9 %) threatened.

AbstractThe karyotype of Zingel zingelfrom the Morava River (Czech Republic) was analyzed. The diploid chromosome number was 2n=48 in females and 2n=47 in males, however, one large unpaired metacentric chromosome was present in males. This proves to be the X1X1X2X2/X1X2Y multiple sex chromosome system developed from the fusion of two sub- or acrocentric chromosomes where a sex chromosome Y was present as one of them.

The lower reaches of the River Dyje were heavily modified between 1975 and 1985. The river was straightened, isolating its meanders and reducing its length by 22%. As a consequence, the river bed showed a markedly lower diversity in both hydrological and morphological characteristics. Because the River Dyje forms the state boundary between the Czech Republic and Austria, fluvial activity of the lower reaches is excluded. Along the River Dyje an active alluvium has been preserved, with approximately 1300 hectares in the Czech Republic and somewhat less in Austria. The flow regime in the lower reaches is regulated by 19 water reservoirs and a number of fishponds, with a total capacity of approximately 45% of the annual drainage. These modifications have distinctly impacted the living conditions of the indigenous ichthyofauna. Based on the results of our ichthyological investigations from 1994 to 2000, we have recommended a number of modifications that could improve the environmental conditions for fishes: (i) controlled flooding of the alluvial meadows, aimed at creating conditions for the spawning of phytophilous fish species; (ii) restoration of permanent connections between separated river meanders and the River Dyje to increase the hydrological and morphological diversity in the river bed; (iii) creation of artificial pools in the floodplain to provide more suitable habitats for fishes. Copyright © 2003 John Wiley & Sons, Ltd.

The lower reaches of the River Dyje were heavily modified between 1975 and 1985. The river was straightened, isolating its meanders and reducing its length by 22%. As a consequence, the river bed showed a markedly lower diversity in both hydrological and morphological characteristics. Because the River Dyje forms the state boundary between the Czech Republic and Austria, fluvial activity of the lower reaches is excluded. Along the River Dyje an active alluvium has been preserved, with approximately 1300 hectares in the Czech Republic and somewhat less in Austria. The flow regime in the lower reaches is regulated by 19 water reservoirs and a number of fishponds, with a total capacity of approximately 45% of the annual drainage. These modifications have distinctly impacted the living conditions of the indigenous ichthyofauna. Based on the results of our ichthyological investigations from 1994 to 2000, we have recommended a number of modifications that could improve the environmental conditions for fishes: (i) controlled flooding of the alluvial meadows, aimed at creating conditions for the spawning of phytophilous fish species; (ii) restoration of permanent connections between separated river meanders and the River Dyje to increase the hydrological and morphological diversity in the river bed; (iii) creation of artificial pools in the floodplain to provide more suitable habitats for fishes. Copyright © 2003 John Wiley & Sons, Ltd.