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Not AvailableAn experiment of 65 days duration was conducted to study the effect of biofilm formed on different natural substrates at different substratum densities on the growth and survival of juveniles of freshwater prawn Macrobrachium rosenbergii (de Man, 1879). Natural substrates like dried paddy straw and cut grass were evaluated as substratum for biofilm production. The experiment was conducted in fiber glass tanks of 500 l capacity. The study comprised six treatments viz., dried paddy straw at 60 (T1); 120 (T2) and 240 (T3) g tank-1 and cut grass at 60 (T4) and 120 (T5) g tank-1 , each with three replicates following a completely randomised design. Prawn juveniles reared without any substratum acted as control. Ten days after the introduction of substratum in the tanks, prawn juveniles (2.01 g±0.37) were stocked at a density of 40 m-³. The juveniles were fed with 2 mm commercial pellet feed (30% protein) at 5% of the biomass. No water exchange was done in the treatment tanks whereas in control tanks 50% water exchange was done once every week. The study revealed significantly (p<0.05) higher survival rate (%) in the treatment tanks (94.4±9.6, 80.5±12.7, 86.1±12.7, 86.1±4.8 and 91.6±8.35 for treatments T1, T2, T3, T4 and T5 respectively) compared to the control (52.8±9.5). Among treatment tanks, T2 and T3 showed significantly higher (p<0.05) average daily growth (g d-1) (0.055±0.005 and 0.057±0.005 respectively) when compared to other treatments (0.0367±0.02 for T1 and 0.0373±0.01 for T5). But the specific growth rate did not show any significant difference among the treated groups including control. Use of biofilm significantly reduced the usage of water (by 2.9 times) compared to control, which is significant considering the predicted water scarcity in future.Not Availabl

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Not AvailableFor natural ecosystems as well as human development, freshwater bodies like reservoirs are critically important. Krishnagiri reservoir, a moderately impacted tropical reservoir of India, is an important source of freshwater. However, eutrophication status due to anthropogenic activities is a major threat to this reservoir. This endeavour aimed to determine the spatio-temporal differences for selected (21) limnological parameters along with trophic status of Krishnagiri reservoir for its sustainable management. Samples (water and plankton) were collected from 11 sites covering entire reservoir during pre-monsoon, monsoon and post-monsoon season. Limnological parameters showed some spatio-temporal variations, the season has more impacts on water quality than sites as evidenced by cluster analysis. Principal component analysis distinguished the seasons based on major influencing water quality parameters. The reservoir trophic status fluctuated from eutrophic to hyper-eutrophic. Water quality index showed that the reservoir falls under unsuitable category. Additionally, cyanobacterial bloom formation was observed in all the seasons, with dominance of Microcystis sp. This investigation can be used as a baseline for studies pertaining to nutrient and sediment loading, and immediate action is required for employment of integrated management plan to restore this aquatic ecosystem. The study also recommends strategies for sustainable management of the aquatic bioresources.Not Availabl

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Not AvailableFish assemblage structure in Palair reservoir, a medium tropical reservoir along the river Paleru, a tributary of river Krishna in Southern India, was studied along the spatial gradient of the impoundment. The abundance and assemblage structure of wild fish aggregated around the fish cage units installed in the reservoir were assessed and compared with other sites. Seasonal sampling was carried out and fish community structure in terms of species composition and abundance, trophic guild, niche, tolerance, resilience and conservation status were analyzed. A total of 38 fish species were recorded wherein the family Cyprinidae dominated in the number of species (15) followed by Cichlidae and Channidae (3 each). Margalef richness index (d), Pielou’s evenness index (J’), Simpson’s index (1-λ) and Shannon index (H’) revealed significant variation across different zones. Species richness was maximum in the Site1 (d = 4.44–5.12), whereas the abundance of individuals was maximum at Site4 (H’ = 2.65–2.86) i.e. near cage in the lacustrine zone. The important species contributing to the dissimilarities among the zones were identified and percentage of their contribution was estimated using SIMPER analysis. Trophic guild of fishes indicated the dominance of omnivorous species followed by carnivores, indicating the heterotrophic phase of the reservoir. The spatial and seasonal variations in the fish assemblage structure were tested applying statistical analyses such as PERMANOVA and nMDS. The results indicated a positive impact of cage farming in supporting the wild fish fauna, influencing the large aggregations of fishes around the cages. The temporal variability in the cage-associated fish assemblage was related to recruitment periods of juveniles (e.g. E. maculates and E. suratensis in summer, and S. seenghala in monsoon seasons). The links between fish assemblages and environmental parameters were explored through DISTILM and the deterministic factors for fish abundance in the reservoir were phosphate, pH, dissolved Oxygen, total hardness and depth. The study also indicated the impacts of cage culture with record of accidental escapes of farmed fish to the reservoir system. The baseline information generated and recommendations formulated in the study are crucial for the conservation of fish diversity, fisheries enhancement and management planning of tropical peninsular reservoirs.Not Availabl

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Not AvailableThe pattern of a fish assemblage of a large reservoir, Stanley (also called as Mettur) in Peninsular India was studied to derive various management protocols, specifically fish enhancement. The investigation was carried out in the spatial and temporal scale of the reservoir during 2017–2019. A total of 52 species belonging to 35 genera were recorded indicating high species richness. Simpson (0.17), Shannon (0.17), dominance (0.104), and evenness (0.52) indices did not show significant differences among zones whereas there was a significant difference during different seasons. On a temporal scale, maximum species were recorded in monsoon (47) followed by post-monsoon (43) and pre-monsoon season (33). On a spatial scale, it represented that riverine (47) and transitional zone (37) showed more species richness compared to lacustrine zone (30). Based on the catch structure of this reservoir, it is evident that exotic fishes play a major role in the recent past. One species under critically endangered and endangered, three species under near threatened, and two under vulnerable species were observed in the catch during this study period. The trophic guild of fishes showed the dominancy of planktivores. Abiotic factors such as temperature, pH, and chlorophyll were found directly influencing the species abundance. The study suggested management measures, including observation of closed fishing season, protection of breeding grounds, use of fish aggregating devices, mesh size regulation, and fish seed stocking in the reservoir.Not Availabl