Stanislav Lusk

Alien fish species in the Czech Republic and their impact on the native fish fauna

Abstract. 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.

Huchen in the Czech Republic: A review

Abstract This paper focuses on the historical and present occurrence of huchen, Hucho hucho (L.), in the Czech Republic. The last autochthonous huchen specimens caught in Moravia at the end of the nineteenth century are discussed, as are huchen stocking and and success rates in the Czech Republic from the late nineteenth century to the present, catches of trophy-sized recreational angling catches of huchen, and the results of measures taken to re-introduce the species to traditional areas of occurrence and to introduce it to new ones. The occurrence of huchen at present is confirmed in some sections of the Labe, Oder, and Morava river basins within the Czech Republic, and all of these populations are sustained through stocking material obtained through artificial reproduction. No self-sustaining huchen populations have been identified anywhere in this region.

The X1X1X2X2/X1X2Y multiple sex chromosome system in the Zingel zingel (Pisces: Perciformes) from the Morava River (Czech Republic)

Abstract The karyotype of Zingel zingel from 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.

Non-native fish species in River Odra and Morava basins in the Czech Republic

Abstract 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 gibelio and 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 melanostomus and Proterorhinchus semilunaris were the last ones which have arrived there by themselves. Coregonus maraena and Coregonus peled are bred in fishponds. The basic part of the non-native fishes’ spectrum existing in free waters of the two basins consists of the species which are bred in aquaculture and fishponds (Oncorhyncus mykiss, Salvelinus fontinalis, Ctenopharyngodon idella, Hypophthalmichthys molitrix, and Hypophthalmichthys nobilis). These species, with the exception of Hypophthalmichthys molitrix and Hypophthalmichthys nobilis, introduced also into the fishing grounds and especially Oncorhynchus mykiss and Ctenopharyngodon idella make the important fishes for anglers. Their presence in the waters of the Czech Republic might be considered as beneficial from the economic point of view. From the ecological point of view, the im- portant fact is that they have become very well acclimatised in the local conditions and their natural breeding does not take place and their distribution in water ecosystems, as well as their numbers are fully determined by the management of the Czech Anglers Union. However, Carassius gibelio, Pseudorasbora parva and also Lepomis gibbosus in the River Morava basin have been assessed as distinctly invasive species having more negative impacts on the original ichthyocenosis and biodiversity. Neogobius melanostomus is also potentially dangerous in this basin. In the case of spread of Lepomis gibosus into the River Odra basin, it might become also potentially highly dangerous.

The current threat level of fish in river network of individual sea-drainage areas in the Czech Republic

Abstract 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. The most important reasons considered as the causes of the disappearance or reduction in the presence of some fishes are the water pollution, adjustments to water flow beds, the limitation of floods in alluvial areas, the permanent river basin fragmentation, and the spread of invasive species. Out of these factors, the only positive change has been noticed in the pronounced decrease in water flow pollution after 1990. Angling is also considered as the set of targeted bio manipulation which purposefully and often one-sidedly influences fish populations for the benefit of species being interesting for the angling sport.