Dyje River Research Articles

Diet of two invading gobiid species (Proterorhinus semilunaris and Neogobius melanostomus) during the breeding and hatching season: No field evidence of extensive predation on fish eggs and fry

Abstract One of the potential impacts of invasive gobies on native fish fauna is predation on eggs and fry. Therefore, the diet composition of two invading gobiid species, the tubenose goby Proterorhinus semilunaris and round goby Neogobius melanostomus, was examined in the Dyje river system (Danube basin, Central Europe) during the 2011 reproductive season to ascertain the extent of gobiid predation on heterospecific and conspecific eggs and juveniles. Consumption of fish eggs and juveniles by invading gobies was very low. The diets of both species consisted largely of benthic macroinvertebrates, and particularly insect larvae. These results indicate that invading gobies in the Dyje river system are likely to impact native fish fauna more through competitive effects than through direct predation on eggs and juveniles.

Freshwater molluscs of the Dyje (Thaya) River and its tributaries - the role of these water bodies in expansion of alien species and as a refuge for endangered gastropods and bivalves

The malacofauna of the Dyje River, including the lower sections of its five tributaries, is still rich and diversified despite the pollution, regulation and building of several dam reservoirs. In total, 42 freshwater mollusc species (24 gastropods, 18 bivalves) were found at 75 sites. The richest malacofauna (30 species) was recorded in the lower section of the Dyje. Populations of endangered or rare molluscs Theodoxus danubialis, Viviparus acerosus, Lithoglyphus naticoides, Unio crassus, Pseudanodonta complanata, Pisidium amnicum and P. moitessierianum were found. The first three species inhabit only the area under study in the Czech Republic. Especially the occurrence of Unio crassus corresponds with river sections that were only partly affected by human activities (long distance below dam reservoirs, less polluted sections, unregulated watercourses). The occurrence of five invasive species, four originating from other continents (Potamopyrgus antipodarum, Physella acuta, Ferrissia fragilis, Sinanodonta woodiana) and one (Dreissena polymorpha) originally Ponto-Caspian, was confirmed for the Dyje River and its tributaries. The Dyje River formed the main invasion route from the Danube River into Moravia (eastern part of the Czech Republic).

Trace metal contamination of the Dyje River stretch between Znojmo and Nové Mlýny, Czech Republic

The analyses of seven trace metals (Hg, Zn, Ni, Cr, Cu, Pb, Cd) in the water, bottom sediments, macroinvertebrates and fish tissues were conducted at two localities on the Dyje River, Czech Republic, at different distances downstream from the Znojmo Reservoir (at 12 and 31 km) to evaluate a contamination level. The maximum admissible limits were exceeded in Hg in the water and in the case of Ni in bottom sediments at both localities and also in Hg in zoobenthos sample at locality further from the reservoir. In regard to trace metal contamination of fish tissues, it was found that safe limits for mercury, cadmium and lead were not exceeded. Mercury and cadmium contents have declined markedly since the 1990s, but the amount of lead has increased. Human consumption of fish caught in the Dyje River is most limited by concentration of Hg in the fish muscle. The maximum tolerated intake was set as high as 3.80 kg per week.

The influence of changes to abiotic parameters on the fish assemblage structure of a lowland stream

Ichthyological monitoring and the assessment of 16 physical and chemical parameters of the water environment were conducted at two localities on the Dyje River, Czech Republic, at different distances downstream from the Znojmo Reservoir (at 12 and 31 km) to reveal habitat alterations. Canonical correspondence analysis confirmed that differences in fish abundance between localities were influenced by different hydrological regimes characterized by discharge and flow velocities and also by water conductivity, which increased with the distance from the reservoir. The influence of chemical parameters of water related to water quality on fish assemblage structure was insignificant. The second locality (further from the reservoir) was characterised by substantial water shortage during the vegetation season. Changes in hydrological regime and the loss of connectivity in the Dyje River both connected with dam building and water shortage for irrigation have led to dramatic changes in the fish assemblage structure since the 1950s and the complete loss of common nase.

Seasonal dynamics of mosquito occurrence in the Lower Dyje River Basin at the Czech-Slovak-Austrian border

During 2009–2011, a total of 45 two-day captures of mosquitoes (Insecta: Diptera: Culicidae) were made at six sites in the Lower Dyje River Basin. Trapping was performed from early April through the end of October using Centers for Disease Control and Prevention (CDC) miniature light traps baited with carbon dioxide (CO2). In total, 415,218 female mosquitoes belonging to six genera and 30 species were captured. In early April, only small numbers of wintering species females (Culex pipiens s.l., Culiseta annulata and Anopheles maculipennis s.l.) were detected. From mid-April, there was a sharp increase in the occurrence of snow-melt species (Aedes cataphylla, Ae. intrudens and, sporadically, Ae. communis and Ae. leucomelas, totalling 2090 females). Their occurrence peaked in early May, but they gradually ceased flying in during June. Ae. sticticus females also became active starting in late April, while Ae. cantans s.l., Ae. vexans, Ae. rossicus and other species were active from early May. The greatest occurrence of mosquitoes was recorded in summer months (from mid-June through the end of August). In this period, the dominant species were Ae. vexans (49.70–80.20%) and Ae. sticticus (6.14–25.62%). The species Ae. rossicus, Ae. cantans s.l., Cx. pipiens s.l. and Cx. modestus also were very abundant from mid-June to late July. The occurrence of mosquitoes decreased rapidly during September. In the second half of October, only small numbers of Ae. vexans, An. claviger and Cx. pipiens s.l. females were captured, while Ae. cinereus s.l., Ae. rossicus, Ae. sticticus, Cx. modestus, An. maculipennis s.l. and An. plumbeus were seen only very sporadically.

Downstream drift of round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus semilunaris) in their non‐native area

AbstractSeveral Ponto‐Caspian gobiid species have recently expanded their ranges in Europe and North America. This is the first study to demonstrate passive downstream dispersal (drift) of the round goby (Neogobius melanostomus) and tubenose goby (Proterorhinus semilunaris) in newly colonised areas (River Dyje, Danube basin), a factor that could play an important role in their dispersal. Drift duration (i.e. number of dates on which the species was caught) in round goby was longer than that of both native species and tubenose goby, providing a possible advantage. Size of drifting fish was restricted to a narrow range of 6–8 mm and 5–8 mm for round and tubenose goby, respectively. Drift in both species occurred almost completely during hours of darkness (<1 lux) and fish size did not vary throughout the night. In both species, drift density increased significantly during the first hour after dusk. Round goby density gradually decreased up to dawn, while tubenose goby density varied throughout the night with no clear pattern. Drift of early life stages appears to be an important phenomenon that has not received adequate attention in studies of round and tubenose goby ecology and dispersal.

Reservoir to river passage of age‐0+ year fishes, indication of a dispersion pathway for a non‐native species

This study demonstrates passage of age-0+ year individuals of pikeperch Sander lucioperca, common bream Abramis brama and non-native tubenose goby Proterorhinus semilunaris from the Nové Mlýny Reservoir into the River Dyje (Danube River basin, Czech Republic) through the turbine of a hydropower facility. Most fishes had standard length (LS ) in the range 12-33 mm. Seasonal patterns corresponded with spawning activity, i.e. an early single spawning event for S. lucioperca, multiple spawning events for A. brama and continuous spawning with a later start and prolonged duration for P. semilunaris. Sander lucioperca, P. semilunaris and larger A. brama (>22 mm) drifted almost exclusively during the dark; smaller A. brama displayed no preference for light or dark. Proterorhinus semilunaris displayed significantly lower mortality than other species when passing through the turbine (3% compared to 18%). The passage of high numbers of P. semilunaris from the reservoir (estimated at 473 000 individuals per year), and their subsequent mass downstream drift, may have contributed to rapid population establishment along the River Dyje and the quick downstream expansion.

THE RESPONSE OF BENTHIC MACROINVERTEBRATE AND FISH ASSEMBLAGES TO HUMAN IMPACT ALONG THE LOWER STRETCH OF THE RIVERS MORAVA AND DYJE (DANUBE RIVER BASIN, CZECH REPUBLIC)

The lower Morava and Dyje rivers belong among the large lowland rivers on the southeast of the Czech Republic flowing into the Danube 69 km downstream of their confluence. Despite their high nature value and environment protection, both rivers suffered from heavy pollution from the sixties to the eighties of the last century. Significant improvement of their water quality during the last two decades resulted in the partial recovery of former assemblages of both benthic macroinvertebrates and fish. Recently, altogether 262 and 137 taxa of macrozoobenthos were recorded at the Dyje and Morava rivers, respectively. In the River Dyje, 3 and 21 non-native and threatened (according to IUCN categories) invertebrate species, respectively, were ascertained, whilst in the River Morava their numbers were 2 and 10, respectively. The fish assemblage consisted of 23 and 24 species, respectively, plus one hybrid in each of the rivers, bleak being by far the most abundant fish. In the sections under study, several rare and/or protected species were also recorded. Two of them, ide (Leuciscus idus) and burbot (Lota lota) belong among vulnerable fish species and four others, white-eye bream (Abramis sapa), striped ruffe (Gymnocephalus schraetser), streber (Zingel streber) and zingel (Zingel zingel), are considered as critically endangered species. Currently, both lower stretches of the rivers Morava and Dyje have been heavily invaded by round goby, Neogobius melanostomus.

Geoconservation in the Czech Republic and geomorphosites assessment for the geotourism and geoeducation purposes : a case study from podyji national park

The article deals with history, practice and possible future development of geoconservation in the Czech Republic. Both examples of legislative instruments and other geoconservation activities are presented. Podyji National Park represents an exceptionally well preserved example of canyon-like valley of river Dyje with unique land-forms (deep tributaries, meanders, rock walls or block accumulations). However, the geoheritage in Podyji National Park is not very promoted and well-managed. The assessment methodology is presented and according to the results, the proposals for rational use of selected geosites are outlined.

Spatiotemporal differences in tree spatial patterns between alluvial hardwood and mountain fir–beech forests: do characteristic patterns exist?

AbstractQuestionsWhat are the differences between the tree spatial patterns (TSP) of various recruit and mortality waves in alluvial hardwood forests and mountain fir–beech forests? Are there any statistically significant differences between the mean TSP of these forest types? Are these differences stable over time?LocationAlluvial floodplain forests at the confluence of the Morava and Dyje rivers, and mountain fir–beech forests in the Outer Western Carpathians, Czech Republic.MethodsIn both forest types, seven 2‐ha rectangular plots were analysed. The pair correlation function g(r) was used to describe tree density variability of trees with DBH ≥ 10 cm. The analyses were carried out for data sets from the 1970s, 1990s and 2000s. A bootstrap method was used to test for significant differences between the mean values of g(r) from alluvial forests and from fir–beech forests.ResultsRecruits in mountain fir–beech forests revealed consistent clustering to at least 5 m. In alluvial hardwood forests, recruits also showed random distribution as well as occasional regular distribution at distances over 20 m. Bootstrap significance tests revealed significant differences between the mean values of g(r) for alluvial forests and fir–beech forests. Alluvial floodplain forests showed statistically significant stronger clustering up to a distance of 4 m in all study periods. At distances over 20 m, mountain fir–beech forests demonstrated stronger clustering. In the 1970s, this was statistically significant only at a distance of 32 m, but in the 2000s, it was at intervals of 22–30 and 34–38 m.ConclusionsThe methods of data analysis in this study enabled us to find significant features of TSP at finer resolution than the common resulting trichotomy of univariate analysis: clustering, randomness and regularity. We believe that, on the basis of detailed spatial analyses, it is possible to create a TSP model that reflects the typical features of particular forest types.

Winter survival of Phytophthora alni subsp. alni in aerial tissues of black alder

The winter survival of the invasive pathogen Phytophthora alni subsp. alni in black alder stems was studied in the bankside alder stand of the Moravská Dyje River in southern Bohemia after two very different winter seasons: cold in 2008/2009, with the average temperature of –1.96°C, and extremely mild in 2006/2007, with the average temperature of 2.54°C. The difference in these two winters resembles the expected potential climate change in Central Europe in this century. After the cold winter of 2008/2009, the pathogen survived in only 13.91% of the samples, with the average survival rate of 2.70%. The pathogen survived the mild winter much better and was successfully isolated from 86.09% of the samples, with the average survival rate of 25.52%. Moreover, the total thickness of the covering tissues (outer + inner bark) and exposure to the most heated southwestern quadrant of stem girth positively affected the pathogen survival. Winter freezing seems to be an important environmental factor regulating the pathogen survival in alder stems and disease severity.    

Mosquitoes (Diptera: Culicidae) of the Lower Dyje River Basin (Podyjí) at the Czech-Austrian border

Abstract During 2009–2011, mosquitoes were captured in CDC miniature light traps using CO2 (dry ice) at six sites in the Lower Dyje River Basin (Czech Republic). Other methods of capture — sweeping from vegetation and collection of larvae and pupae from ponds — were also used for more precise diagnostics. Thirty mosquito species of six genera were confirmed. A total of 415,218 females were captured. Most frequently found were the outbreak species Aedes vexans (56.52% of all mosquitoes collected) and Ae. sticticus (16.40%). Among other flood species, Ae. rossicus (5.17%), Ae. cantans and Ae. annulipes (2.44% of all females collected), and Ae. cinereus s. l. (1.11%) were especially abundant. Females of Ae. cataphylla were captured in spring (0.31%) and Ae. intrudens was numerous only at one site. Among the other species, Culex pipiens s. l. (6.61%) and Cx. modestus (8.87%) were abundant. Anopheles maculipennis s. l. (1.01%), An. claviger (0.43%), An. plumbeus (0.08%), An. hyrcanus (0.08%), Coquillettidia richiardii (0.52%) and Culiseta annulata (0.18%) were also detected. Sparsely occurring were Ae. excrucians, Ae. flavescens, Ae. caspius and Ae. geniculatus. Captured only very sporadically were Ae. communis, Ae. leucomelas, Ae. dorsalis, Ae. rusticus, Cx. martinii, Cx. territans, Cs. morsitans and Uranotaenia unguiculata.

Paleolithic hunting in a southern Moravian landscape: The case of Milovice IV, Czech Republic

AbstractThe Dolní Věstonice–Pavlov–Milovice area (Czech Republic) on the slopes of the Pavlov Hills provides an opportunity for correlating the geomorphology of the Dyje River valley with Gravettian settlement patterns. Although the sites vary in size and complexity, they create a regular chain of strategic locations at elevations between 200 m and 240 m asl. In 2009, a road collapsed into deserted cellars inside the village of Milovice and revealed a complex of archaeological layers deep within loess, at an elevation of only 175 m asl. This paper presents an analysis of this atypical archaeological site location and compares the results with the other sites. We argue that this location allowed direct contact with mammoth herds concentrated on the floodplain, while the aquatic environment offered possibilities for gathering plants and fishing. This site represents a new aspect of organized settlement, hunting strategies, and short‐distance human movements during the Gravettian within this area. © 2011 Wiley Periodicals, Inc.

Vascular Plants Distribution as a Tool for Adaptive Forest Management of Floodplain Forests in the Dyje River Basin

The study is based on a full floristic inventory of floodplain forests in South Moravia along the upper part of the Dyje River (Forest district Valtice). The study area is located in the Dolni Morava Biosphere Reserve and includes several Sites of Community Importance within Natura 2000. The aim of the inventory was to analyze diversity of herb and woody species occuring in the study area, including both native protected and threatened species, and invasive species. The study area was divided into segments. A segment represented the smallest unit of spatial forest division – “forest stand part”. The species were recorded into a special scratch-list. Altogether, 656 plant species were found. The floristic database has been integrated with GIS. Maps of distribution of selected plant species or groups of plants were produced. On the basis of geographical visualization of the above mentioned results we identified areas with a high diversity of all species and endangered species. The results may be used as a base for adaptive forest and environmental management.

Causes and Consequences of a Flood Wave on the Lower Reach of the Dyje River Near Břeclav

The settlements situated on broad flat floodplains of rivers are threatened by floods during increased water flows in the rivers. The floodplain of the Dyje river situated in the area between the Nové Mlýny water reservoir and Břeclav has been protected from former annual floods since the 70s of the last century due to the water-management measures. The realised measures including the construction of the new floodway protect the town of Břeclav as well. A long-term research into the soil water regime of the floodplain forest is underway in the region. The results obtained document its historical evolution and current status. Only in the early April of 2006 (i.e. after 34 years), an unexpected "flash flood" occurred again due to a specific climatic situation. The combination of the high snow cover in higher parts of the basin and a rapid warming up caused an intensive runoff. The so-called dry polder (floodplain forests, meadows and fields) above Břeclav protected the town and its infrastructure from potential catastrophic consequences.

Flood duration determines the reproduction success of fish in artificial oxbows in a floodplain of a potamal river

Janáč M, Ondračková M, Jurajda P, Valová Z, Reichard M. Flood duration determines the reproduction success of fish in artificial oxbows in a floodplain of a potamal river. Ecology of Freshwater Fish 2010: 19: 644–655. © 2010 John Wiley & Sons A/S.Abstract – Fish reproduction was studied in six man‐made water bodies (borrow pits) adjacent to the channelised Dyje River (Danube basin) over five seasons. Terrestrial vegetation provided spawning and nursery habitats when inundated by raised water levels in the borrow pits (hereafter referred to as ‘floods’). The diversity of 0+ fish and the density of 0+ cyprinids (mainly Abramis bjoerkna, Scardinius erythrophthalmus and Rutilus rutilus) in June–October were positively correlated with flood duration in previous months. The density of 0+ Perca fluviatilis was independent of the flood duration. The density of spawners and predators did not influence the diversity of 0+ fish and the density of 0+ cyprinids. Receding flood and associated lack of shelters resulted in decreasing density of 0+ cyprinids, numbers sometimes decreasing to zero. Prolonged floods facilitated the survival of 0+ fish and resulted in high 1+ cyprinid density in the following season. Specific hydromorphological conditions (e.g., the presence of shallow littoral zone or flooded vegetation) are necessary to enable successful spawning and provide shelters for 0+ fish in artificial water bodies.

Carassius auratus gibelio—The most successful invasive fish in waters of the Czech Republic

Carassius auratus gibelio is considered an alien fish species in the hydrographic system of the Czech Republic. Around 1976, this form immigrated from the River Danube into the confluence of the Morava and Dyje rivers and gradually spread over the hydrographic network over the course of the next 15 to 20 years. Helped by man, this species overcame the boundaries between particular drainage areas, expanding its range and colonising suitable habitats. C. a. gibelio has become fully naturalised and has produced numerous stable populations. This is the only non-indigenous fish species in the Czech Republic showing distinct characteristics of an invasive taxon. Initial populations of C. a. gibelio colonising the new area consisted solely of triploid females. The occurrence of males after 1990 started a process of transformation of the originally monosexual female (triploid) population into a mixed population containing both females and males. At present, males are predominantly diploid, with occasional triploid individuals. Females are predominantly triploid and less frequently diploid. Tetraploid individuals are quite rare. At the Morava-Dyje confluence, the population reproduces both gynogenetically and sexually. C. a. gibelio exerts important competitive, as well as destructive, effects upon the indigenous ichthyofauna. Native species of Carassius carassius and Tinca tinca, previously abundant have vanished from those localities dominated by C. a. gibelio. C. a. gibelio is fished for on hook and line in natural habitats in the Czech Republic, with an annual recorded catch of 25–50 t. Annual production in fishponds varies between 15 and 70 t, yet its marketable utilization is problematic.

Palynology and natural environment in the Pannonian to Holocene sediments of the Early Medieval centre Pohansko near Břeclav (Czech Republic)

Pohansko (Czech Republic) is an important Early Medieval centre of the Great Moravian Empire (9th century AD). The locality has a settlement with archaeological findings from Mesolithic to the modern times. The studied sediments belong to the stream and flood deposits of the Dyje river, aeolian sands and buried soils. The lower parts of some boreholes penetrated into the Upper Miocene sediments. 172 samples were palynologically analysed. The original forest with relative small human impact was observed on the base of Holocene layers. Even sporadic Cerealia pollen were found here. A deforestation was visible in the cultural layer; it is linked with existence of the Great Moravian agglomeration and its fortification. Later, a partial forest reconstruction probably took place in the surroundings. Very abundant pollen of human-exploited plants (cereals, herbs) were discovered in the filling of archeological feature O1. The possible practical potential of rampart also as the flooding protection was indicated by the existence of marshy plants palynomorphs. The existence of oxbow was proved in the excavated probe S3. The lowermost sample was dated by 14C as 7830 ± 60 BP. The findings of Carpinus pollen in the layer dated as Early Atlantic support the earlier spreading of this genus in the Czech Republic (i.e. South Moravia).

Mosquito (Diptera: Culicidae) Surveillance for Arboviruses in an Area Endemic for West Nile (Lineage Rabensburg) and Ťahyňa Viruses in Central Europe

Six viral isolates were obtained from 23,243 female mosquitoes (examined in 513 pools) belonging to 16 species and collected along the lower reaches of the Dyje River in South Moravia (Czech Republic, central Europe) during 2006-2008: five isolates of Orthobunyavirus Tahyna (TAHV, California group, family Bunyaviridae: three isolations from Aedes vexans (Meigen), one from Ae. sticticus (Meigen), one from Culex modestus Ficalbi); and one isolation of Flavivirus West Nile (WNV, Japanese encephalitis group, family Flaviviridae)-strain Rabensburg (proposed lineage 3 of WNV) from Ae. rossicus (Dolbeshkin et al). All viral isolates were recovered from mosquitoes collected in 2006 (15,882 mosquitoes examined), while no virus was isolated from mosquitoes trapped in 2007 and 2008, when 1,555 and 5,806 mosquitoes were examined, respectively. The population density of local mosquitoes was very low in 2007 and 2008 because of warm and dry summer including a considerably low water table, compared with environmental conditions favorable for mosquito development in 2006. The virus isolation procedure was based on intracerebral inoculation of newborn mice. In parallel, more than one-third of the samples (183 pools consisting of 8,470 individual mosquitoes) were also examined by inoculating Vero cell cultures in Leighton tubes. However, the latter method detected only three of the six virus isolates (including WNV-Rabensburg). Ae. rossicus is a new potential vector for WNV-Rabensburg. This species feeds mostly on mammals including man; this raises the question whether this virus lineage is not adapted to an alternative mosquito-mammal cycle in the South-Moravian natural focus.

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

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.