Lakes and Reservoirs: Research and Management最新文献

After five years of impoundment, Bui Reservoir fisheries has evolved with silver catfish, Chrysichthys nigrodigitatus among the most important commercial species. Based on standard length analyses of 162 individuals (62 males, 39 females) from post-impoundment seasonal sampling at three (3) stations, the population structure, well-being, growth type, sex ratio, length at first capture and rates of growth, mortality, exploitation, and other derived parameters of C. nigrodigitatus were estimated to provide requisite information for sustainable management. The population is composed of fewer juveniles and more males than females, with females relatively larger than males (modal size 7.0–7.9 for males and 9.0–9.9 for females). Females were physiologically better than males (79.49% of females had condition factor above 2.0 compared to 53.23% males) notwithstanding seasonal fluctuations. Unimodal length structure was observed for all seasons except for the post-rainy season with 2 modes, all of which, however, indicated a single year class and single spawning. Estimated hypoallometric and hyperallometric growth values among seasons and sexes were not significantly different from the isometric pattern. Estimated von Bertalanffy growth parameters were asymptotic size (L_∞) = 13.07 cm SL, growth constant (K) = 1.01 year,⁻¹ and length at time 0 (t_o) = 0.18. Growth performance index (ϕ') was 2.27, indicating slow growth while the lifespan was 2.73 years. Total mortality, natural mortality, and fishing mortality estimates were high (3.56, 2.44 and 1.12 respectively) while exploitation was below optimum (E = 0.32). Regular assessment of fish population, growth, and other characteristics is recommended to provide requisite information for strategic interventions for sustainable management and development of reservoir fisheries.

This study examines the current state and projected future of India's dams, focusing on the challenges posed by ageing infrastructure, sedimentation, increasing water demands and climate change. With over half of India's major dams now surpassing 50 years of age, the risk of structural deterioration and reduced functionality is escalating. Sedimentation, a critical issue, has led to a substantial decrease in reservoir storage capacity, impacting water availability for agriculture, drinking water and hydropower generation. Additionally, climate change is anticipated to intensify these challenges, with more frequent and severe weather events stressing dams that were not originally designed for such variability. To ensure the longevity and resilience of these structures, comprehensive adaptation measures are essential. Key recommendations include modernising dam infrastructure, implementing advanced sediment management strategies, integrating climate-responsive design features and enhancing real-time monitoring systems. Future research should prioritise climate modelling, innovative sediment control and seismic resilience improvements. Proactive policy, combined with sustained funding and community engagement, is vital to safeguarding India's water resources and addressing the complexities of an evolving environmental landscape.

The species representing minor fisheries are gaining more economic importance as fishing pressure is increasing on major riverine fishes. Population characteristics or demographic studies of minor fishery resources can provide insight into the impact of environmental issues, conservation status, and help in the management and development of fisheries. We studied the population dynamics of two commercially significant fishes, freshwater garfish, Xenentodon cancila and Cangaturi halfbeak, Hyporhampus limbatus, from Ujani water reservoir (Pune, India) using cast net and gill net on a monthly basis for 1 year. Length-weight relationship (LWR) and population dynamics of both fishes were analysed using FAO-ICLARM Stock Assessment Tool (FISAT). LWR analysis revealed a positive allometric growth pattern in both X. cancila (b = 3.12) and H. limbatus (b = 3.15). The estimated potential longevity (t_max) of X. cancila and H. limbatus was 3.48 and 5.76 years, respectively. The observed length at first capture for X. cancila and H. limbatus was 18.53 and 6.66 cm, respectively. Juveniles of H. limbatus face higher exploitation as compared to X. cancila. Higher natural mortality was observed in X. cancila while fishing mortality was higher in H. limbatus. Recruitment analysis revealed two spawning bouts in 1 year for both species. Xenentodon cancila fish stock is under-exploited and H. limbatus fish stock is over-exploited in Ujani reservoir. Further reproductive biology studies are necessary for the effective development and management of fisheries involving X. cancila and H. limbatus.

In this study, length-weight relationships of seven catfish species collected from the middle stretch of the Ganga River in India were determined. The specimens were gathered from the Sadiyapur and Daraganj fish landing centers in this region of the Ganga River between November 2022 and October 2023. Digital callipers and digital balances were utilised to measure the total length (TL) and body weight (BW) of all fish specimens. The growth coefficient b ranged from 1.98 for Sperata aor to 3.31 for Sperata seenghala. Also, Rita rita, Sperata aor, Eutropiichthys vacha, Wallago attu and Bagarius bagarius exhibited negative allometric growth (b < 3) while Sperata seengala and Clupisoma garua showed positive allometric growth (b > 3). The coefficient of determination (R²) values ranged from 0.66 to 0.93 across the seven catfish species. Additionally, the relative condition factor (K_n) value is greater than 1 for all the catfish species, indicating that all the catfish species are in good health.

Fish biodiversity was assessed as a biological indicator of aquatic environmental quality across six wetlands of Lake Tana, Ethiopia. A total of 1616 fish specimens, representing 18 species, four genera and three families, were collected. Labeobarbus intermedius (23.1%–48.9%) and L. brevicephalus (6.7%–44.4%) were the most abundant, whereas L. beso, L. gorguari and L. truttiformis were least common (0%–6.7%). Spatially, Clarias gariepinus dominated at Megech River Mouth (9.4%), and Oreochromis niloticus was abundant at Wonjeta (54.5%) and Ras Abbay (62.5%). Catch Per Unit Effort (CPUE) ranged from below the detection limit to 110.0 fish/h. The Fish Index of Biotic Integrity (FIBI) and Habitat Quality Index (HQI) varied significantly, with the highest FIBI values at Gumara and Megech River Mouths (39.0) and HQI scores peaking at Zewdie Girar (19.0) and Wonjeta (18.5). Multivariate analyses grouped wetlands into three distinct clusters based on the fish assemblage structure: Cluster 1 (Wonjeta, Ras Abbay and Avaj), Cluster 2 (Zewdie Girar and Gumara River Mouth) and Cluster 3 (Megech River Mouth). Principal Component Analysis explained 80.6% of the total variation, whereas Canonical Correspondence Analysis accounted for 98.5% of the variance in fish–environment relationships, identifying water depth, Secchi depth, ammonia, phosphorus and nitrate as key drivers of environmental degradation. Margalef's richness and Hill's diversity indices varied significantly among wetlands, reflecting spatial differences, but showed no significant seasonal variation. Functional feeding group distribution exhibited seasonal shifts, especially among benthic, tolerant and detritivorous species. These findings underscore the ecological importance of Lake Tana's wetlands and the need for targeted conservation measures to sustain fish diversity and habitat integrity.

Major dams in Zimbabwe are losing more than half of their design capacity in the first 11 to 12 years of operation. Despite these obvious impacts of sedimentation in the country's reservoirs, sedimentation studies have only been conducted once for 90% of the reservoirs. Thus, a sedimentation estimation study was conducted in November 2014 in Lake Chivero to quantity storage loss due to sedimentation, determine the spatial distribution of sediment deposition in the reservoir, update its elevation-capacity curves and estimate its useful life. The study used a dual beam echo sounder for determining depth measurements. Depth measurements were converted to digital elevation models in a Geographic Information System environment. A comparison of the 1953 and 2014 digital elevation models indicated that the lake was losing depth uniformly. The highest deposition depths were observed towards the dam wall and the deep central parts of the lake along the old river channel. Minimal sediment deposition was generally observed at the shallower parts of the lake, on the north-east and south-western locations. A total of 49126170.34 m³ (18%) of the lake's storage capacity has been lost to sedimentation, which translates to an average annual capacity loss of 792,357 m³ year⁻¹ (0.295% per year) since construction in 1953. The lake's specific sediment yield and remaining useful life were calculated at 352.31 m³ year⁻¹ km⁻² and 106.63 years; respectively. This loss of storage in the lake will impact the operational and economic benefits for which it was built. It will also affect the habitats of its varied flora and fauna. In the absence of original topographic maps produced at the inundation, the dual frequency echo sounder can be used to generate data to estimate sediment loads into the reservoir as well as update elevation-capacity curves.

Wetland ecosystems in the Himalayan region face growing threats from climate change, human activities and environmental degradation. This study introduces an integrated approach to assess and predict the water quality index (WQI) for effective wetland management, focusing on the Alital and Bandatal Lakes in Nepal's Sudurpaschim Province. These lakes were selected due to their distinct ecological and geographical characteristics, as well as differing levels of human impact. A total of 40 water samples (20 from each lake) were collected, and 16 physicochemical parameters, including turbidity (Tur.), total dissolved solids (TDS) and major ions were analysed. Hydrochemical properties were characterised using graphical methods, such as the Gibbs and Piper diagrams and the WQI was computed using the arithmetic average method. The hydrochemical facies analysis indicated that carbonate weathering was the dominant process in both wetlands, with Bandatal showing significant anthropogenic influence. The findings revealed that Alital maintained ‘Excellent’ to ‘Good’ water quality, with an average TDS of 64 mg/L and Tur. of 2.14 NTU, reflecting minimal human impact. In contrast, Bandatal exhibited ‘Poor’ to ‘Unsuitable’ WQI classifications, with TDS averaging 115 mg/L and Tur. reaching 63.6 NTU, highlighting substantial human influences. An artificial neural network (ANN) model was developed to predict the WQI, demonstrating outstanding accuracy with an R² of 0.99 for both the training and testing phases. These results underscore the potential of the ANN model for proactive wetland management, aligning with sustainable development goals (SDGs) related to clean water and ecosystem restoration and providing globally applicable insights for wetland conservation.

The assessment of nutrient and heavy metal accumulation in lake sediments is essential for understanding their role in the ecohydrological dynamics of lake ecosystems, as sediments can function both as a sink and source of nutrients, metals and various contaminants aquatic ecosystem. The main objective of this study was to evaluate the concentrations of nutrients and heavy metals and their accumulation in the sediments across different sampling locations of Loktak Lake and to compare them against geochemical background values and sediment quality guidelines. The key findings of the study revealed substantial nutrient accumulation in sediments from the Keibul Lamjao National Park site, which can be attributed to the decomposition of organic matter from dense floating vegetative masses called ‘Phumdis’. Iron concentrations in sediments were significantly high, ranging from 909.83 to 1004 mg/kg and its enrichment is likely due to diffused surface runoff from the iron-rich soils from the surrounding catchment entering the lake through feeder rivers and other anthropogenic influences. The average metal concentrations were in the order of Fe > Mn > Zn > Cu, and all values were below the average shale concentrations and the Interim freshwater Sediment Quality Guidelines (ISQG) set by the Canadian Council of Ministers of the Environment (CCME). The evaluation of the heavy metal pollution status of the lake sediments based on various pollution indices such as the contamination factor, degree of contamination, modified degree of contamination, geoaccumulation index, pollution load index and potential ecological risk index, suggested an overall low level of metal pollution in the sediments of Loktak Lake. The findings of this study provide a crucial baseline for understanding on the sediment-associated nutrient and metals dynamics in Loktak Lake which can aid in the formulation of long-term lake management strategies for preserving the ecological integrity and health of this precious lake ecosystem of the region.