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Papers by Herwig Waidbacher

Research Square (Research Square), Dec 5, 2019

EGU General Assembly Conference Abstracts, Apr 1, 2012

ABSTRACT Isoscapes are spatial maps of the distribution of isotopes on Earth. As a basis for ecol... more ABSTRACT Isoscapes are spatial maps of the distribution of isotopes on Earth. As a basis for ecological studies such as long distance migrations of animals or for determining the origin of food these tools are increasingly being developed, until now - mainly for terrestrial systems. In contrast, in case of aquatic systems only few maps were established up to now. As far as variation in the isotopic distribution in a studied area exists, the isotopic composition bears the potential to be used as natural tracer e.g. for ecological questions or food authentication. Above all the 87Sr/86Sr ratio taken up from the environment by organisms without any significant fractionation is known to provide a direct link to geologically distinct regions. Within the 'IsoMark' project (www.isomark.at), a database ('Isoscape Austria') containing all available spatially explicit isotope data (terrestrial and aquatic) with a focus on isotope distributions in Austrian rivers is being developed. Water samples from different rivers, mainly along the Danube in Austria, were collected and analyzed for their elemental and Sr isotopic composition. Analyses of water samples yielded several 'Isozones' along the Austrian part of the Danube, indicating diverse geology in these river catchments. Studying migration phenomena of fish using natural isotopic marks in hard parts is especially possible between these 'Isozones'. In geologically similar regions with little differences, element distributions or artificial marking methods (tagging, spiking) can serve as additional means. A significant positive relationship between the 87Sr/86Sr ratio in river water and the proportion of siliceous geological formations in the catchment was found on a national and European level. These analyses proved the possibility to predict the 87Sr/86Sr ratios in river catchments all over Europe. This relationship allows for an estimation of the applicability of the 87Sr/86Sr ratio for fish ecological questions on a European scale like migration, homing and dispersal that can hardly be studied with other methods.

Research Square (Research Square), Jan 3, 2020

Frontiers in Environmental Science

Macrophytes play an important role in shallow lakes if large standing crop can be achieved. Here ... more Macrophytes play an important role in shallow lakes if large standing crop can be achieved. Here we stress the role of submerged macrophytes for benthic-pelagic coupling in the shallow oxbow lake Alte Donau (Austria) during restoration triggered by sufficient light availability (12% surface ambient light, photic>12% depth, zoptimum) in both, the benthic and the pelagic habitat. Focusing on zoptimum, rather than on minimum light requirement (euphotic depth), seemed to be more meaningful to follow the macrophyte development. After phosphate precipitation treatment, the photic>12% pelagic habitat accounted for more than half of the total water volume in summer, while the achievement of the same photic>12% conditions for half of the total sediment surface area was delayed by 8 years. A delay of light exposure on the lake bottom area compared to the lake water volume is given by the basin morphometry, but the time span that is required for passing this delay depends on the effic...

XXV Congresso Nazionale SOIPA, 2008

Livestock Research for Rural Development

The effects of substituting hydrolysed feather meal (HFM) for freshwater shrimp meal (FSM; Caridi... more The effects of substituting hydrolysed feather meal (HFM) for freshwater shrimp meal (FSM; Caridina nilotica, Roux) on growth, digestibility and survival in Nile tilapia (Oreochromis niloticus L.) were evaluated under laboratory and practical culture conditions. Fingerlings with mean ranges of 26.0-26.5 and 35.4-37.0 g were held indoor in aquaria with recirculating water, and in cages that were installed in 800 m 2 fertilized pond, respectively. Five isocaloric (12.3 kJ g -1 ) diets, containing between 28.5 and 31.0 % of crude protein, were prepared by gradually substituting HFM for FSM at rates of 0, 25, 50, 75 and 100% and fed to fish in aquaria; tilapia in cages were fed diets at substitution levels 0, 50 and 100%. All fish were fed at 10 % of body weight day -1 in three replicates for 84 days. Results indicated that substitution of HFM for FSM at levels above 50% led to significant (P<0.05) growth reductions in aquaria. However, even 100% substitution rate did not significant...

Molecular Ecology, 2001

Mitochondrial haplotype diversity in 27 populations of brown trout, Salmo trutta L., in Austria w... more Mitochondrial haplotype diversity in 27 populations of brown trout, Salmo trutta L., in Austria was investigated by sequencing the 5′ end of the mitochondrial DNA (mtDNA) control region. Although all populations are within the Danube drainage, 44% of all individuals carried Atlantic basin haplotypes. It is argued that the presence of these haplotypes in Austria primarily reflects introgression stemming from the stocking of hatchery‐reared fish. However, several lines of evidence suggest that some natural colonization from Atlantic lineages may have contributed to the present haplotype diversity. Nonetheless, the more diverse Danubian clade is represented by regionally distinct haplotype diversity that should be protected from the continued introduction of domesticated strains of exogenous fish.

Archiv für Hydrobiologie, Dec 19, 2003

River regulation, urban development and the construction of a hydroelectric power plant have cons... more River regulation, urban development and the construction of a hydroelectric power plant have considerably changed the ecological condition of the Danube section in Vienna. In 1997, the previously straight shoreline of the Danube in this area was reconstructed by creating shallow water areas, coves, gravel banks and side channels. These inshore structures were created to increase habitat diversity in this area and to establish, together with existing ponds, a system of stepping stone biotopes, which serve as migration linkage through the municipal area of Vienna. A monitoring programme (1998-2001) was established to assess the functional integrity of these structures. A multi-species-approach using odonates, amphibians, and fish was developed to cover aquatic, amphibious and terrestrial habitat components. As demonstrated in this study, rehabilitation of heavily altered systems may play an important role in improving ecologically degraded areas and in reconnecting isolated landscape patches. A new metric (Floodplain Index) was applied for defining an ecological management objective, for characterizing the newly created structures and for assessing habitat heterogeneity.

Joint Danube Survey 3 - A Comprehensive Analysis of Danube Water Quality, 2015

According to the demands of the European Union Water Framework Directive, natural structures and ... more According to the demands of the European Union Water Framework Directive, natural structures and habitats were implemented during the construction of the hydropower plant Freudenau. Ecological data were processed and evaluated from the years 1999 to 2000 as well as from the years 2003 till 2004. The study area was divided into five parts, which were further divided into 19 habitats. The statistical software SPSS (© SPSS Inc. 2007) was used for statistical analysis. The dominances after Tischler were calculated and consulted for further analysis. In the context of this project an increase in the number of fish species from 1993 to 2004, showing a peak before and after the power station construction, was demonstrated. The CPUE values proved high magnitudes in the habitats B, D and I. The lowest number of individuals shows the Free Flowing Stretches. Both juvenile and adult fish could be proved in many habitats. A more exact analysis with the dominances after Tischler confirmed previou...

BackgroundMicroorganisms inhabiting the gut play a significant role in supporting fundamental phy... more BackgroundMicroorganisms inhabiting the gut play a significant role in supporting fundamental physiological processes of the host, which contributes to their survival in varied environments. Several studies have shown that altitude affects the composition and diversity of intestinal microbial communities in terrestrial animals. However, little is known about the impact of altitude on the gut microbiota of aquatic animals. The current study examined the variations in the gut microbiota of Nile tilapia (Oreochromis niloticus) from four lakes along an altitudinal gradient in Ethiopia by using 16S rDNA Illumina MiSeq high-throughput sequencing. ResultsThe results indicated that low-altitude samples typically displayed greater alpha diversity. The results of principal coordinate analysis (PCoA) showed significant differences across samples from different lakes. Firmicutes was the most abundant phylum in the Lake Awassa and Lake Chamo samples whereas Fusobacteriota was the dominant phylum...