Browsing by Author "Leichtfried, M."

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A comparative analysis on the effects of river discharge on trophic interactions in two tropical streams.
(International Review of Hydrobiology, 2017) Weliange, W.S.; Amarasinghe, U.S.; Vijverberg, J.; Leichtfried, M.; Füreder, L .
Discharge-mediated seasonal patterns of food web interactions were investigated in two streams in Sri Lanka; Eswathu Oya (a perennial wet-zone stream) and Yan Oya (a seasonal dry-zone stream). Based on volumetric proportions of diet composition, relative abundance of fish species and their daily food rations, the mean cumulative consumption of each prey taxon was estimated for each fish population. Food web diagrams were prepared using trophic index of fish, trophic class of prey and feeding interactions between fish and prey. Both streams showed seasonal patterns of discharge due to rainfall, but no significant effect was evident in the trophic index of most fish species. In both streams, cumulative consumption of prey taxa was highest during low discharge regime due to increased abundance of both prey taxa and consumers. In Eswathu Oya, diversity of prey taxa was higher during the low discharge regime, but in Yan Oya, high diversity occurred during the high discharge regime. Herbivorous and/or detritivorous fish species were rare in Eswathu Oya but dominant in Yan Oya. Complex food web structure in Yan Oya due to high fish species richness and high diversity of prey categories made it less sensitive to discharge extremes in contrast to relatively simple food web structure in Eswathu Oya. This study, therefore, highlights the importance of maintaining the quality of riparian environments for conservation of biodiversity.
Comparison of trophic structure of fish assemblages in two tropical steams in Sri Lanka: a seasonal dry zone stream and a perennial wet zone stream
(International Review of Hydrobiology, 2019) Weliange, W.S.; Amarasinghe, U.S.; Vijverberg, J.; Leichtfried, M.; Füreder, L.
Most tropical rivers especially in the Asian region, are severely impacted by various human perturbations, and the diverse habitats in streams support rich invertebrate and vertebrate communities. It is hypothesized that the fish assemblages and their dietary structure in two tropical streams differ because they flow through different terrains and are exposed to different climatic conditions. In the wet zone stream, which is geomorphological more complex, fish faunal diversity showed significant longitudinal variations, and sustains endemic fish species. In the diets of fish, taxonomic composition was different along the longitudinal gradients, but dietary taxa richness in the two streams was virtually similar having 32 dietary taxa in wet zone stream and 36 taxa in dry zone stream. In the wet zone stream, we observed a lower proportion of specialist feeding species than those in the dry zone stream. Trophic indices of individual species in fish assemblages ranging from herbivory to carnivory also indicate structuring of fish communities along the longitudinal gradients of the two streams based on dietary structure. The main differences between the fish assemblages in the wet zone compared to the dry zone were the higher number of endemic species and the lower percentage of specialist feeders with higher trophic indices. The outcome of this study hopefully contributes to plan future biodiversity conservation management schemes under various river basin development strategies.
IRESA – Initiative of river ecology in Sri Lanka: from Science to application
(Sri Lanka Association for Fisheries and Aquatic Resources, 2005) Fureder, L.; Leichtfried, M.; Amarasinghe, U.S.; Weliange, W.S.
Longitudinal variation of benthic macroinvertebrate communities in two contrasting tropical streams in Sri Lanka.
(International Review of Hydrobiology, 2017) Weliange, W.S.; Leichtfried, M.; Amarasinghe, U.S.; Füreder, L.
The benthic macroinvertebrate fauna and main abiotic parameters were studied to understandthe patterns of diversity and structure along the temporal and longitudinal gradients in twotropical lotic ecosystems in the wet and dry zones of Sri Lanka. Invertebrate abundance (annualmeans) was in the same magnitude in the two streams (2,520 ind. m−2in the wet zone streamand 2,940 ind. m−2in the dry zone stream). Both streams had similar annual mean diversity levelsmeasured as Shannon diversity (Eswathu Oya (wet zone) = 2.11; Yan Oya (dry zone) = 2.07),with a mean annual evenness (Pielou evenness) of 0.56 ± 0.14 for Eswathu Oya and 0.60 ± 0.09for Yan Oya. Along the longitudinal gradient, abundance and taxa richness increased toward thelower reaches in the wet zone stream but decreased in the dry zone stream. Composition offunctional feeding groups was greatly influenced by abiotic factors in the temporal gradient thanin the longitudinal gradient. This was possibly due to the seasonal patterns of flow regimes, andallochthonous nutrient inputs into the streams. Hence, resource management and conservationas well as attempts of ecological assessment in tropical streams should be based not only on thein-stream characteristics but also on the catchment properties.