Over the past 150 years, the waters of the Czech Republic were experimentally stocked or invaded by a total of 41 alien (non-native) fish species. The following species have become fully naturalized and produced self-sustained populations: Carassius gibelio, Pseudorasbora parva, Ameiurus nebulosus and Gasterosteus aculeatus, which produced stable populations in several spatially limited localities. In some cases Oncorhynchus mykiss, Salvelinus fontinalis and Coregonus maraena will produce instable temporary populations based on released material obtained from fish farms and ponds. The occurrence of the remaining acclimatized alien species (Coregonus peled, Ctenopharyngodon idella, Hypophthalmichthys molitrix, Aristichthys nobilis) in natural ecosystems and fishponds depends on stocking fish obtained from artificial spawning and cultures. The documented annual average production of alien species fit for human consumption amounts to around 2 000 tonnes, i.e. 8.2 % of the annual average production of marketable fish cultures in the Czech Republic. A significant negative impact of the introduced species on native ichthyofauna has been ascertained as regards its ecological, biological properties, biodiversity and health. Considered a typical invasive alien species, Carassius gibelio heavily depressed the occurrence and numbers of indigenous Carassius carassius populations and also contributed to the decreased numbers of Tinca tinca, Leucaspius delineatus and other native cyprinid fish. P. parva and A. nebulosus show a much weaker and limited impact. The introduction of C. idella was accompanied by the introduction of the tapeworm species, Bothriocephalus gowkongensis, which subsequently caused heavy losses in cultures of Cyprinus carpio. In 2008, Neogobius melanostomus was recorded for the first time in this country at the confluence of the Morava and Dyje rivers.
To this day five Gobio gobio subspecies in northern, western and central Anatolia, in Turkey have been classified. Some subspecies were described based on 2-4 specimens by B a t t a l g i l (1942, 1944), L a d i g e s (1960), B ă n ă r e s c u & N a l b a t (1973), B ă n ă r e s c u (1992), B ă n ă r e s c u (1999). In this study, Gobio gobio specimens from the type localities of various running waters and lakes of norht, norhwest and central Anatolia were collected and ANOVA (analysis of variance), cluster analysis and canonical discriminant analysis were applied to fifty variables (eight meristic and forty-two metric characters derived from thirty-four measured or counted variables) to show the main differences between them. From these statistical analyses, Gobio gobio specimens were placed in one of three groups: G1 Beyşehir Lake; G2 Sakarya River Basin, Gerede and Melendiz Stream; G3 İnsuyu Stream, southwards from Tuz Lake. Measurements Standard length/Head height (SL/hH), Head length/Head height (C/hH), Standard length/Head length (SL/C), Predorsal distance/Postdorsal distance (pD/poD), Standard length/Postdorsal distance (SL/poD) and Standard length/Predorsal distance (SL/pD) were important characteristics for distinguishing the populations of Gobio gobio.
The population and genetic profiles of a remnant Vimba vimba population in the upper course of the River Dyje (N=48°53 ́18 ́ ́/ E=15°39 ́29 ́ ́) was carried out to provide a basis for conservation measures. This population is an isolated fragment of a more widespread population in this river system and is now declining. It came into being 60 years ago as a consequence of the construction of the Vranov dam in the middle section of the River Dyje. Over those 60 years V. vimba disappeared from the other localities of the River Dyje basin. In the population under study, vimba is a single-batch spawner involving two age groups of fishes (4 to 5 years of the age). Individuals over six years of age are rare and sporadically occurring fishes of 8 to 10 years are exclusively females. The size of the adult part of population is less than one thousand individuals. The length growth rate is relatively high as compared with other studied populations in the Czech Republic, fishes of five years attain 200 mm of Sl. A very low genetic variability was evidenced in the population (mean number of alleles per locus = 1.30 ± 0.1; percentage of polymorphic loci = 16.7 %; mean observed heterozygosity = 0.022 ± 0.011).
The comparative craniological analysis of the short-barb Crimean gudgeon from the Chernaya River (south-western Crimea) and G. gobio from the Volga River basin, as well as the study of morphological cahracters used for identification of G. gobio carpathicus natio krymensis by B e r g (1949) and G. gobio kovatschevi by B ă n ă r e s c u et al. (1999) resulted in conclusion about the specific status of G. krymensis. Several craniological characters, namely the relative lengths of supracleithra and cleithra, preopercle width and the modal numbers of pores in several bones, are presumed to be available characters for its identification, as well as barbel length.
This study describes the of distribution and level of endangerment of the genus Gobio in Croatia. Four species of the genus Gobio live in the Croatian Danube River basin: Gobio Gobio - common gudgeon, G. albipinnatus - whitefin gudgeon, G. kesslerii - sand gudgeon and G. uranoscopus - stone gudgeon, while in the Croatian Adriatic Sea basin lives only G. Gobio. According to IUCN methodology and the level of endangerment, in the Red List of Threatened Plants and Animals of Croatia G. Gobio is considered to be of the least concern (LC). G. uranoscopus and G. kesslerii are in the category of near threatened (NT) while G. albipinnatus is considered as data deficient (DD).
Thee species of the genus Gobio occur in the hydrographical network of the Czech Republic, belonging to the basins of three seas (the North, black, and Baltic seas). G. Gobio is distributed over streams belonging to all three sea basins. It is most common in their middle reaches, which are inhabited by fish communities of the Barbus-Chondrostoma type. Compared to that past, the population numbers of this species have not undergone any marked changes. G. kesslerii occurs only in the Bečva River (a tributary to the Morava River) and in the Morava River upstream of the mouth of the Bečva River (danube basin, Black Sea). G. albipinnatus is distributed over the Morava and Dyje rivers and their tributaries (Danube basin, Black Sea). Compared to a century ago, the extent of distribution of G. albipinnatus has dropped to about 50%, which is due chiefly to stream canalisation and water pollution. At present, G. albipinnatus has been ascertained in the lower part of the River Labe, yet there are some doubts as to the originality of this occurrence. The localities of G. albipinnatus and/or G. kesslerii are shared with G. Gobio, with which they hybridise. No evidence is available of the occurrence of G. uranoscopus (Agassiz, 1828) in the Czech Republic, although it does occur in neighbouring Slovakia and Austria. The most important devastation factors, which limited the distribution of the gudgeon in the past, include the construction and operation of dams and weirs, stream canalisation and water pollution. National laws project G. kesslerii as critically endangered and G. albipinnatus as endangered. Both species are listed in European conservation laws (Council Directive no. 92/43/EEC) and, therefore, special areas of conservation have been delimited for them within the NATURA 2000 system.
The following species of the genus Gobio occur in the Tisza River drainage area in Slovakia: G. Gobio, G. kesslerii, G. albipinnatus and G. uranoscopus. G. Gobio is the commonly distributed species. It occurs in streams of various sizes, attaining the largest numbers in streams populated by the barbel type fish communities. It occurs together with other Gobio spp., whith which it can produce hybrids. The present occurrence of G. Gobio has not changed basically from that in the past. G. albipinnatus occurs primarily in lowland streams, both in large rivers and canalised minor streams and channels. The distribution of this species in the Tisza River drainage area in Slovakia has not, appreciably changed from that in the previous period. According to earlier data, G. kesslerii was relatively abundant in the middle and upper reaches of a number of streams. At present the occurrence of this species has been confirmed in just a few localities so that its range has been markedly restricted. In some cases, however, the species may have been mistaken for G. albipinnatus. According to literary data, G. uranoscopus occurred in the past mainly in the upper reaches of rivers Torysa (the Hornád River drainage area), Topľa, Ondava, Laborec, and Uh (the Bodrog River drainage area). This species shows the most marked decrease in range, compared to that in the past. in recent times its presence has been confirmed only in a few localities. The devastating factors that have affected the distribution of the particular Gobio spp. include water pollution, stream and bed canalisation, decreased river bottom diversity, extraction of gravel materials, and hydro-energetic constructions (steps, weirs and dams). of the above gedgeon species, G. uranoscopus and G. kesslerii are protected by the national legislation in Slovakia. In accordance with the EU legislation (Council Directive 92/43/EEC), special protection regions (NATURA 2000) are being defined for G. uranoscopus, G. albipinnatus, and G. kesslerii.