Lakes and Reservoirs: Research and Management最新文献

The Western Ghats region (part of Western Ghats-Sril Lanka biodiversity hotspot) in India, is known not only for its rich ichthyodiversity and endemism but also as a region that continues to face various human pressure on its freshwater ecosystem through over-exploitation, habitat destruction and alien fish invasion. Insufficient data regarding the demographics and exploitation pattern of threatened freshwater fishes in the Western Ghats (WG) region serves as a barrier to effectively managing and conserving these species in a sustainable manner. In this study, growth, mortality and exploitation level of an endemic and threatened cyprinid, Hypselobarbus kolus were investigated based on the specimen collected by tribal fishers through small-scale fishery in Poringalkuthu Reservoir, Chalakudy River, WG, India. The asymptotic length (L∞) and growth rate (K) (growth parameters) of H. kolus were estimated as 341.25 mm and 0.64 year⁻¹ respectively. The potential longevity (t_max) and length at first capture (L_c) were found to be 4.69 years and 249.34 mm respectively. The fishing mortality (F = 1.20 year⁻¹) of H. kolus was higher than the natural mortality (M =.65 year⁻¹) suggesting an unsustainable level of exploitation for the species within the present study area. Current exploitation rate is greater than E₅₀ and 68% of the predicted maximum exploitation (E_max) points out the possibility of uncertain future of the stock under current exploitation rate. An integrative conservation approach, including fishing closure during spawning seasons, mesh size regulation, quotas system for local tribes and fishermen will ensure to sustainable harvesting for the species in the WG hotspot.

Inland fisheries are a source of fish as well as livelihoods for as many as 82% of the total 28 million engaged in the Indian fisheries sector. Reservoir fisheries are a significant component but remain largely untapped, both as a potential resource for development as well as a site of academic interest. The importance of institutional arrangements in governing natural resources is fairly recognized. However, empirical examination of how governance regimes interact with and impact the economic benefits from natural resource extraction for its principal actors is less explored, at least in the Indian context. Through case studies of two uniquely located and differently governed fisheries of Gandhi Sagar (GS, Madhya Pradesh) and Rana Pratap Sagar (RPS, Rajasthan) reservoirs in the Chambal River valley, it investigates the (in)equity in benefit sharing among labour (fishers), capital (fishing contractor), and the management (custodian-state). Neither a purely revenue model of reservoir fisheries governance in RPS nor a seemingly revenue cum welfare model in GS has enhanced the income of nearly 2590 small-scale fishers above their subsistence levels, though the latter provides welfare benefits to its 2209 dependent fishers through cooperatives. Of the gross annual income of INR 13,874/ha in GS and INR 16,126/ha in RPS, the fishers have only one-third share in both cases, while the fishing contractors have 22% (GS) and 34% (RPS), and the resource managers have 29% (GS) and 15% (RPS) share, with the remaining 15% (GS) and 18% (RPS) accounted for by other costs, making the benefit sharing arrangement inequitable for fishers. Two key reforms, immediate market-linked upward revision of sale-price at which fish caught by fishers are collected by the contractors (from INR 33/kg to INR 65/kg), and long-term organization of fisher cooperatives as empowered collectives able to exercise their agency and co-manage the resource, are essential to ensure the fishers do not become captive labourers.

One of the largest wetlands in Bangladesh's north-east, Hail Haor supports a variety of aquatic habitats and has a diversified ecosystem. To ascertain the fish diversity indices of Hail Haor, this study was carried out month by month from December 2020 to June 2021. For this study, three sampling sites in the Moulvi Bazar district—Chiruadobi Beel, Gopla River and Balla Beel were chosen from which fish samples were collected. Twenty-five different fish species were identified and 12,076 fish (individual numbers) were counted and categorized. The Shannon diversity index varied from 1.33 to 1.65. Hail Haor's species diversity index is moderate by the index standard. The Shannon evenness index (E) varied from .41 to .51. The Depressed Community is present in the Hail Haor species diversity index, as per the index standard. The Simpson dominance index fluctuated from .56 to .72. The species diversity index of Hail Haor contains moderate dominance, as per the index standard. With the help of local retailers, fishers, and other relevant stakeholders, the FGD identified factors that have an impact on the diversity index. The current study on diversity indices will be highly beneficial for formulating strategy and managing Hail Haor by strictly adhering to the recommendations.

Anthropogenic litter (AL) in world's aquatic ecosystems presents critical ecological threats to environmental quality, aquatic biodiversity and human welfare. However, most studies on AL have been conducted in marine ecosystems with very little focus being given to freshwater systems like Lake Victoria. This study characterized AL pollutants in Dunga beach in Lake Victoria, Kenya, where sampling was done in the beach, riparian and benthic zones along a 100 m reach for 6 days. Across the sampled reaches, the AL associated with packaging, consumer products, building and construction, transport, electronic wastes, textile, fishery and medical materials were collected, counted, sun-dried and weighed. AL were more abundant in the beach and riparian zone than in the benthic reaches with plastics being the dominant litter in all reaches. Based on Kruskal–Wallis rank sum test the density of AL associated with packaging and consumer products was significantly higher than other AL in all the reaches. Plastics, polystyrene and glass wastes dominated the beach zone at 31.19%, 12.14% and 11.14%, respectively. In the benthic area, the dominant wastes were plastics, fishery and polystyrene items at 22.14%, 16.34% and 12.14%, respectively. The top 10 AL pollutants in Dunga beach were as follows: bags/food wrappers, bottle caps, diapers, plastic and glass beverage bottles, plastic plates, forks, knives, spoons, straws and e-wastes. Based on data from literature, several clear patterns emerged when comparing relative AL abundance across other aquatic habitats. In the Lake Michigan Beach, the AL were dominated by plastics (41.2%) followed by cigarettes at 29.3%. In contrast, Chicago River Beach contained more glass wastes (42.1%) while Chicago River Riparian had more plastics (57.8%). At the South Sea of Korea, fishing gear wastes were the majority AL (61.1%). AL consisting of fishing items was restricted to benthic and riparian settings, in which the benthic zone had the most items recorded. It is therefore evident that a large amount of AL waste accumulates at Dunga, Hippo point and other beaches in the world, thus justifying the need for beach cleaning and maintenance strategies. This study presents baseline data that is useful to environmental ecologists, aquatic scientists and management authorities to formulate policies, evaluate guidelines and recommend beach management strategies to conserve aquatic biodiversity, human health and aesthetic value of the freshwater habitats.

The present study presents selected water quality parameters and the levels of heavy metals in water, sediments and Nile tilapia (Oreochromis niloticus) of Lake Nakuru. Nine sediments and nine water samples, as well as 30 specimens of Nile tilapia, were collected from the northern part of the lake. Physical parameters were measured in situ using multiple probes and metres. Heavy metals were analysed using an atomic absorption spectrophotometer (AAS). The pH, dissolved oxygen concentration, temperature, salinity and electrical conductivity ranged from 9.52 to 9.72, 4.58 to 8.62 mg/L, 23.40°C to 25.7°C, 2.39‰ to 2.81‰ and 4470–5226 μs/cm, respectively. Heavy metal levels (mean ± SD) were generally low in the water samples. Chromium values ranged between 7.16 and 9.19 mg/kg dw in sediment samples, and between 3.7 and 13.06 mg/kg dw in fish samples. Lead values ranged between 12.5 and 31.04 mg/kg dw in sediment samples and 4.06 and 9.95 mg/kg dw in fish samples. Arsenic values ranged between 9.5 and 21.7 mg/kg dw in sediments and below detectable limit to 2.11 mg/kg dw in fish samples. Mercury values ranged between .14 and .31 mg/kg dw in sediment samples and .12 and .35 mg/kg dw in fish samples. Cadmium was the only heavy metal concentration that was below the detection limit in the three matrices. Significant differences were observed for some heavy metal concentrations in water, sediments and fish across sites (p < .05). The levels of lead and chromium in fish were above the East African Standard, World Health Organization and European Union limits. The results of the present study recommend a possible reclassification of the lake, an immediate ban on fish harvesting and consumption from Lake Nakuru and a policy intervention on the fishery and pollution management.

Water is a scarce resource globally, and a water shortage worldwide would cause water security. Although there is plenty of literature studying water security, many discuss water security concerning water quality that is harmful to human health, some on the floods and droughts which destroy agriculture and livelihoods of people, and others on water war or water conflict in transboundary river basin; but little discusses water security concerning changing river flow, volume, inundation, productivity and livelihoods in the river–lake system (RLS). Thus, this paper studies the RLS to examine how changes in river flows and the volumes of the water in the RLS would affect the inundation and productivity of the RLS and, later, the livelihoods of river–lake people (RLP). In answering this question, the article undertakes the literature review and the case study of Tonle Sap Lake (TSL) in Cambodia to examine this form of water security. The paper concludes that the RLS has a close relationship between the flow, volume, inundation and productivity of fisheries and people's livelihoods. The hydropower dams, urban development and climate change cause the disconnectivity and the discontinuity of the river–lake flow, volume and inundation, undermining the productivity of fisheries and livelihoods of river–lake-dependent communities. There is a strong need for cooperation and coordination between riparian states in the Mekong River Basin (MRB) to maintain the secured flow and volume in the Mekong River (MR) and TSL and protect the livelihoods of RLP.

Biofloc technology (BFT) has gained popularity recently as the aquaculture industry faces significant economic losses due to water pollution creating various pathogens. Many bacterial, viral and fungal diseases in fish cause a decrease in annual world fish production. Therefore, owing to a growing demand for healthy fish, zero-water exchange is widely practiced in fish and shellfish production. It minimizes the release of aquaculture wastewater into the aquatic ecosystem, which contains nutrients, organic matter and pathogens. It uses a minimal amount of land, which provides an impartial cost–benefit ratio to maintain socio-economic sustainability. Besides sustainability, fish cultured in the BFT have also expressed better health status after being challenged by different pathogens. However, this review explores the use of BFT as a sustainable approach to wastewater utilization and fish and shellfish production. Apart from this, the review highlights the potential of BFT to enhance fish production in aquaculture systems and discusses various factors that affect the performance of systems, such as carbon-to-nitrogen ratios, aeration and the use of probiotics. It also investigates the role of biofloc in improving water quality, fish and shellfish health prophylactic properties, and its effect on gut microflora. The review further examines the economic feasibility of BFT and discusses about the cost-effectiveness of implementing systems and the potential for generating additional revenue through the sale of bioflocs as a value-added product. Overall, this review highlights the potential of BFT as a sustainable solution for wastewater utilization and increasing fish production. It provides valuable insights into the factors affecting the performance of BFT systems and suggests areas for further research and development in this field.

Lake Jipe, is a shared water resource between Kenya and Tanzania located at the East African Coast is under multiple pressures. The present study assessed the current state of Lake Jipe and its biodiversity dilemma. Random sampling was conducted at 14 sampling points set at equidistant parallel to each other. Sampling depths and location coordinates were measured using Solar Transducer and GPSMAPS® 65 s. In situ water quality parameters were measured using YSI Pro Plus multiparameter; water samples for nutrients analysis were collected and preserved in cooler boxes prior transportation to Kenya Marine and Fisheries Research Institute (KMFRI) laboratory for analysis according to ALPHA 2005. Socio-economic data in relation to status of Lake Jipe ecology were generated using Key Informants Interviews at identified beaches along Kenya and Tanzania. Present findings indicated that the lake has receded from the original 108.72 Km² to 27.32 Km² with annual temperatures, dissolved oxygen and conductivity of 28.58 ± 0.95, 5.19 ± 00 and 799.24 ± 69.41, respectively, for dry season. Wet season recorded 31.21 ± 0.31, 4.16 ± 0.01 and 882.44 ± 57.41 for temperature, dissolved oxygen and conductivity, respectively. Agricultural activities have significantly (90%) contributed to the lake levels decline and further affected the lakes' aquatic biodiversity. Among the most affected are the commercially important endemic fish species of the lake of which Oreochromis jipe has experienced the greatest decline. Overfishing, use of illegal unreported and unregulated fishing gears, intensified fishing along protected fish breeding areas as well as poor management and uncoordinated conservation efforts have significantly contributed to the decline of fish catches from 348 kg of O. jipe in 2016 to 90 kg daily catches in 2022. Consequently, the lake is in the verge of extinction if no action is taken. This calls for awareness on the significance of the L. Jipe ecosystems and its immediate and long-term benefits. Further, there is need to revive and promote alternative economic activities including sustainable aquaculture and agriculture to local communities.

The present study presents the length–weight relationships of five brackish water fish species from the coastal region of West Bengal for which this relationship not known to the present time, including Stigmatogobius sadanundio, Brachygobius nunus, Microphis cuncalus, Butis melanostigma and Puntius vittatus. The slope (b) value of the regression ranges between 2.551 and 3.319, with high correlation values (r² ≥ .943). The relative condition factor (K_n) was also calculated, being >1.0 for all species examined in the present study, indicating of the overall condition of the fish species.

Lake Beseka (Metahara), formerly, an alkaline soda lake in the Central Rift Valley of Ethiopia is recently undergoing unprecedented changes. The objective of this study was to investigate the current status on the plankton composition of Lake Beseka, in relation to the lake's environmental parameters. Samples for physicochemical and biological parameters were taken twice a year during both the rainy and dry seasons at two different sites (open and shore). Temperature, pH, conductivity, dissolved oxygen, alkalinity, salinity, ammonia, silica and soluble reactive phosphate showed significant variation (p < .05) between wet and dry seasons. The physicochemical parameters recorded during this study shows decreasing trend than the previous studies indicating the lakes ecosystem undergone fundamental changes over time. A total of 25 phytoplankton and 13 zooplankton genera were identified. The phytoplankton community of Lake Beseka had previously been dominated by Arthrospira fusiformis, but this time it was completely missing, and diatoms substituted for it. The decrease in pH and salinity of the lake's water could be responsible for these changes. In addition, cyclopoid copepods now predominate over zooplankton in Branchionus dimidiatus during periods of high salinity. Redundancy analysis showed that SRP, ammonia, nitrate and turbidity are important environmental factors that significantly influenced plankton abundance. This study provides new baseline information on the plankton composition of Lake Beseka, in relation to the lake's environmental parameters, which can be used to evaluate future community structure.