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Author: search.filters.author.Weliange, W.S.Subject: search.filters.subject.freshwater fish

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    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.
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    Seasonality in Dietary Shifts in Size-Structured Freshwater Fish Assemblages in Three Reservoirs of Sri Lanka
    (Environmental Biology of Fishes, 2003) Weliange, W.S.; Amarasinghe, U.S.
    We studied seasonal changes in feeding habits of size-structured fish assemblages in three freshwater reservoirs in Sri Lanka. We obtained fish samples for diet analysis from three reservoirs during the months of rising water level (RIWL) and receding water level (REWL). During RIWL, peripheral areas with terrestrial/semi-terrestrial macrophytes get inundated, which resulted in increased food availability for macrophyte feeding fish. During REWL, detrital food sources increase due to decaying terrestrial plant material, which has inundated. Based on the dietary habits of individual species in the three reservoirs during RIWL and REWL, it is evident that detritivorous and phytoplanktivorous fish species, which belong to low trophic levels do not show significant variation in dietary habits between the two seasons (e.g. Oreochromis mossambicus, Oreochromis niloticus and Amblypharyngodon melettinus). Stenophagous species such as benthic invertebrate predators (Puntius chola and Puntius dorsalis), macrophytophagous species (Etroplus suratensis and Tilapia rendalli) and zooplanktivorous Hemirhamphus limbatus do not exhibit significant variation in dietary habits between seasons. Also their feeding habits do not vary with body size. Euryphagous species such as Puntius filamentosus on the other hand, exhibit variations in dietary habits between seasons as well as with body size. Stenophagous species, which feed on detritus and phytoplankton and euryphagous species, which exhibit temporal dietary plasticity, are therefore abundant in fish assemblages of these reservoirs.